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[xonotic/d0_blind_id.git] / d0_blind_id.c
index 1059ffe..3abfb9d 100644 (file)
@@ -1,9 +1,53 @@
+/*
+ * FILE:       d0_blind_id.c
+ * AUTHOR:     Rudolf Polzer - divVerent@xonotic.org
+ * 
+ * Copyright (c) 2010, Rudolf Polzer
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTOR(S) ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTOR(S) BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $Format:commit %H$
+ * $Id$
+ */
+
 #include "d0_blind_id.h"
 
 #include <stdio.h>
 #include <string.h>
 #include "d0_bignum.h"
-#include "sha1.h"
+#include "sha2.h"
+
+// our SHA is SHA-256
+#define SHA_DIGESTSIZE 32
+const char *sha(const unsigned char *in, size_t len)
+{
+       static char h[32];
+       d0_blind_id_util_sha256(h, (const char *) in, len);
+       return h;
+}
 
 // for zero knowledge, we need multiple instances of schnorr ID scheme... should normally be sequential
 // parallel schnorr ID is not provably zero knowledge :(
 #define SCHNORR_BITS 20
 // probability of cheat: 2^(-bits+1)
 
-#define SCHNORR_HASHSIZE 3
-// cannot be >= SHA_DIGEST_LENGTH
+#define SCHNORR_HASHSIZE SHA_DIGESTSIZE
+// cannot be >= SHA_DIGESTSIZE
 // *8 must be >= SCHNORR_BITS
+// no need to save bits here
 
 #define MSGSIZE 640 // ought to be enough for anyone
 
@@ -31,26 +76,37 @@ struct d0_blind_id_s
        d0_bignum_t *schnorr_s;
 
        // public data (player ID public key, this is what the server gets to know)
-       d0_bignum_t *schnorr_4_to_s;
-       d0_bignum_t *schnorr_4_to_s_signature;
+       d0_bignum_t *schnorr_g_to_s;
+       d0_bignum_t *schnorr_H_g_to_s_signature; // 0 when signature is invalid
+       // as hash function H, we get the SHA1 and reinterpret as bignum - yes, it always is < 160 bits
 
        // temp data
-       d0_bignum_t *rn; // random number blind signature
+       d0_bignum_t *rsa_blind_signature_camouflage; // random number blind signature
+
        d0_bignum_t *r; // random number for schnorr ID
-       char xnbh[SCHNORR_HASHSIZE]; // init hash
-       d0_bignum_t *e; // challenge
+       d0_bignum_t *t; // for DH key exchange
+       d0_bignum_t *g_to_t; // for DH key exchange
+       d0_bignum_t *other_g_to_t; // for DH key exchange
+       d0_bignum_t *challenge; // challenge
+
+       char msghash[SCHNORR_HASHSIZE]; // init hash
        char msg[MSGSIZE]; // message
        size_t msglen; // message length
 };
 
 #define CHECK(x) do { if(!(x)) goto fail; } while(0)
 #define CHECK_ASSIGN(var, value) do { d0_bignum_t *val; val = value; if(!val) goto fail; var = val; } while(0)
+#define MPCHECK(x) do { if(!failed) if(!(x)) failed = 1; } while(0)
+#define MPCHECK_ASSIGN(var, value) do { if(!failed) { d0_bignum_t *val; val = value; if(val) var = val; else failed = 1; } } while(0)
+
+#define USING(x) if(!(ctx->x)) return 0
+#define REPLACING(x)
 
 static d0_bignum_t *zero, *one, *four, *temp0, *temp1, *temp2, *temp3, *temp4;
 
-void d0_blind_id_INITIALIZE()
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_INITIALIZE(void)
 {
-       d0_bignum_INITIALIZE();
+       CHECK(d0_bignum_INITIALIZE());
        CHECK_ASSIGN(zero, d0_bignum_int(zero, 0));
        CHECK_ASSIGN(one, d0_bignum_int(one, 1));
        CHECK_ASSIGN(four, d0_bignum_int(four, 4));
@@ -59,11 +115,12 @@ void d0_blind_id_INITIALIZE()
        CHECK_ASSIGN(temp2, d0_bignum_int(temp2, 0));
        CHECK_ASSIGN(temp3, d0_bignum_int(temp3, 0));
        CHECK_ASSIGN(temp4, d0_bignum_int(temp4, 0));
+       return 1;
 fail:
-       ;
+       return 0;
 }
 
-void d0_blind_id_SHUTDOWN()
+void d0_blind_id_SHUTDOWN(void)
 {
        d0_bignum_free(zero);
        d0_bignum_free(one);
@@ -95,7 +152,7 @@ fail:
        return NULL;
 }
 
-BOOL d0_dl_generate_key(size_t size, d0_bignum_t *G)
+D0_BOOL d0_dl_generate_key(size_t size, d0_bignum_t *G)
 {
        // using: temp0
        if(size < 16)
@@ -117,22 +174,24 @@ fail:
        return 0;
 }
 
-BOOL d0_rsa_generate_key(size_t size, const d0_bignum_t *e, d0_bignum_t *d, d0_bignum_t *n)
+D0_BOOL d0_rsa_generate_key(size_t size, const d0_bignum_t *challenge, d0_bignum_t *d, d0_bignum_t *n)
 {
        // uses temp0 to temp4
        int fail = 0;
        int gcdfail = 0;
-       if(size < 16)
-               size = 16;
        int pb = (size + 1)/2;
        int qb = size - pb;
+       if(pb < 8)
+               pb = 8;
+       if(qb < 8)
+               qb = 8;
         for (;;)
        {
                CHECK(d0_bignum_rand_bit_exact(temp0, pb));
                if(d0_bignum_isprime(temp0, 10) == 0)
                        continue;
                CHECK(d0_bignum_sub(temp2, temp0, one));
-               CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, e));
+               CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, challenge));
                if(!d0_bignum_cmp(temp4, one))
                        break;
                if(++gcdfail == 3)
@@ -152,7 +211,7 @@ BOOL d0_rsa_generate_key(size_t size, const d0_bignum_t *e, d0_bignum_t *d, d0_b
                if(d0_bignum_isprime(temp1, 10) == 0)
                        continue;
                CHECK(d0_bignum_sub(temp3, temp1, one));
-               CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, e));
+               CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, challenge));
                if(!d0_bignum_cmp(temp4, one))
                        break;
                if(++gcdfail == 3)
@@ -162,15 +221,106 @@ BOOL d0_rsa_generate_key(size_t size, const d0_bignum_t *e, d0_bignum_t *d, d0_b
 
        // n = temp0*temp1
        CHECK(d0_bignum_mul(n, temp0, temp1));
-               
-       // d = e^-1 mod (temp0-1)(temp1-1)
+
+       // d = challenge^-1 mod (temp0-1)(temp1-1)
        CHECK(d0_bignum_mul(temp0, temp2, temp3));
-       CHECK(d0_bignum_mod_inv(d, e, temp0));
+       CHECK(d0_bignum_mod_inv(d, challenge, temp0));
        return 1;
 fail:
        return 0;
 }
 
+D0_BOOL d0_rsa_generate_key_fastreject(size_t size, d0_fastreject_function reject, d0_blind_id_t *ctx, void *pass)
+{
+       // uses temp0 to temp4
+       int fail = 0;
+       int gcdfail = 0;
+       int pb = (size + 1)/2;
+       int qb = size - pb;
+       if(pb < 8)
+               pb = 8;
+       if(qb < 8)
+               qb = 8;
+        for (;;)
+       {
+               CHECK(d0_bignum_rand_bit_exact(temp0, pb));
+               if(d0_bignum_isprime(temp0, 10) == 0)
+                       continue;
+               CHECK(d0_bignum_sub(temp2, temp0, one));
+               CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, ctx->rsa_e));
+               if(!d0_bignum_cmp(temp4, one))
+                       break;
+               if(++gcdfail == 3)
+                       return 0;
+               ++gcdfail;
+       }
+       gcdfail = 0;
+        for (;;)
+       {
+               CHECK(d0_bignum_rand_bit_exact(temp1, qb));
+               if(!d0_bignum_cmp(temp1, temp0))
+               {
+                       if(++fail == 3)
+                               return 0;
+               }
+               fail = 0;
+
+               // n = temp0*temp1
+               CHECK(d0_bignum_mul(ctx->rsa_n, temp0, temp1));
+               if(reject(ctx, pass))
+                       continue;
+
+               if(d0_bignum_isprime(temp1, 10) == 0)
+                       continue;
+               CHECK(d0_bignum_sub(temp3, temp1, one));
+               CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, ctx->rsa_e));
+               if(!d0_bignum_cmp(temp4, one))
+                       break;
+               if(++gcdfail == 3)
+                       return 0;
+               ++gcdfail;
+       }
+
+       // ctx->rsa_d = ctx->rsa_e^-1 mod (temp0-1)(temp1-1)
+       CHECK(d0_bignum_mul(temp0, temp2, temp3));
+       CHECK(d0_bignum_mod_inv(ctx->rsa_d, ctx->rsa_e, temp0));
+       return 1;
+fail:
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_longhash_destructive(unsigned char *convbuf, size_t sz, unsigned char *outbuf, size_t outbuflen)
+{
+       size_t n, i;
+
+       n = outbuflen;
+       while(n > SHA_DIGESTSIZE)
+       {
+               memcpy(outbuf, sha(convbuf, sz), SHA_DIGESTSIZE);
+               outbuf += SHA_DIGESTSIZE;
+               n -= SHA_DIGESTSIZE;
+               for(i = 0; i < sz; ++i)
+                       if(++convbuf[i])
+                               break; // stop until no carry
+       }
+       memcpy(outbuf, sha(convbuf, sz), n);
+       return 1;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_longhash_bignum(const d0_bignum_t *in, unsigned char *outbuf, size_t outbuflen)
+{
+       static unsigned char convbuf[1024];
+       size_t sz;
+
+       CHECK(d0_bignum_export_unsigned(in, convbuf, sizeof(convbuf)) >= 0);
+       sz = (d0_bignum_size(in) + 7) / 8;
+       CHECK(d0_longhash_destructive(convbuf, sz, outbuf, outbuflen));
+       return 1;
+
+fail:
+       return 0;
+}
+
 void d0_blind_id_clear(d0_blind_id_t *ctx)
 {
        if(ctx->rsa_n) d0_bignum_free(ctx->rsa_n);
@@ -178,52 +328,74 @@ void d0_blind_id_clear(d0_blind_id_t *ctx)
        if(ctx->rsa_d) d0_bignum_free(ctx->rsa_d);
        if(ctx->schnorr_G) d0_bignum_free(ctx->schnorr_G);
        if(ctx->schnorr_s) d0_bignum_free(ctx->schnorr_s);
-       if(ctx->schnorr_4_to_s) d0_bignum_free(ctx->schnorr_4_to_s);
-       if(ctx->schnorr_4_to_s_signature) d0_bignum_free(ctx->schnorr_4_to_s_signature);
-       if(ctx->rn) d0_bignum_free(ctx->rn);
+       if(ctx->schnorr_g_to_s) d0_bignum_free(ctx->schnorr_g_to_s);
+       if(ctx->schnorr_H_g_to_s_signature) d0_bignum_free(ctx->schnorr_H_g_to_s_signature);
+       if(ctx->rsa_blind_signature_camouflage) d0_bignum_free(ctx->rsa_blind_signature_camouflage);
        if(ctx->r) d0_bignum_free(ctx->r);
-       if(ctx->e) d0_bignum_free(ctx->e);
+       if(ctx->challenge) d0_bignum_free(ctx->challenge);
+       if(ctx->t) d0_bignum_free(ctx->t);
+       if(ctx->g_to_t) d0_bignum_free(ctx->g_to_t);
+       if(ctx->other_g_to_t) d0_bignum_free(ctx->other_g_to_t);
        memset(ctx, 0, sizeof(*ctx));
 }
 
-void d0_blind_id_copy(d0_blind_id_t *ctx, const d0_blind_id_t *src)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_copy(d0_blind_id_t *ctx, const d0_blind_id_t *src)
 {
        d0_blind_id_clear(ctx);
-       if(src->rsa_n) ctx->rsa_n = d0_bignum_mov(NULL, src->rsa_n);
-       if(src->rsa_e) ctx->rsa_e = d0_bignum_mov(NULL, src->rsa_e);
-       if(src->rsa_d) ctx->rsa_d = d0_bignum_mov(NULL, src->rsa_d);
-       if(src->schnorr_G) ctx->schnorr_G = d0_bignum_mov(NULL, src->schnorr_G);
-       if(src->schnorr_s) ctx->schnorr_s = d0_bignum_mov(NULL, src->schnorr_s);
-       if(src->schnorr_4_to_s) ctx->schnorr_4_to_s = d0_bignum_mov(NULL, ctx->schnorr_G);
-       if(src->schnorr_4_to_s_signature) ctx->schnorr_4_to_s_signature = d0_bignum_mov(NULL, src->schnorr_4_to_s_signature);
-       if(src->rn) ctx->rn = d0_bignum_mov(NULL, src->rn);
-       if(src->r) ctx->r = d0_bignum_mov(NULL, src->r);
-       if(src->e) ctx->e = d0_bignum_mov(NULL, src->e);
-       // TODO xnbh, msg, msglen?
+       if(src->rsa_n) CHECK_ASSIGN(ctx->rsa_n, d0_bignum_mov(NULL, src->rsa_n));
+       if(src->rsa_e) CHECK_ASSIGN(ctx->rsa_e, d0_bignum_mov(NULL, src->rsa_e));
+       if(src->rsa_d) CHECK_ASSIGN(ctx->rsa_d, d0_bignum_mov(NULL, src->rsa_d));
+       if(src->schnorr_G) CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_mov(NULL, src->schnorr_G));
+       if(src->schnorr_s) CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_mov(NULL, src->schnorr_s));
+       if(src->schnorr_g_to_s) CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_bignum_mov(NULL, src->schnorr_g_to_s));
+       if(src->schnorr_H_g_to_s_signature) CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_bignum_mov(NULL, src->schnorr_H_g_to_s_signature));
+       if(src->rsa_blind_signature_camouflage) CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_bignum_mov(NULL, src->rsa_blind_signature_camouflage));
+       if(src->r) CHECK_ASSIGN(ctx->r, d0_bignum_mov(NULL, src->r));
+       if(src->challenge) CHECK_ASSIGN(ctx->challenge, d0_bignum_mov(NULL, src->challenge));
+       if(src->t) CHECK_ASSIGN(ctx->t, d0_bignum_mov(NULL, src->t));
+       if(src->g_to_t) CHECK_ASSIGN(ctx->g_to_t, d0_bignum_mov(NULL, src->g_to_t));
+       if(src->other_g_to_t) CHECK_ASSIGN(ctx->other_g_to_t, d0_bignum_mov(NULL, src->other_g_to_t));
+       memcpy(ctx->msg, src->msg, sizeof(ctx->msg));
+       ctx->msglen = src->msglen;
+       memcpy(ctx->msghash, src->msghash, sizeof(ctx->msghash));
+       return 1;
+fail:
+       d0_blind_id_clear(ctx);
+       return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_keys(d0_blind_id_t *ctx, int k)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_key_fastreject(d0_blind_id_t *ctx, int k, d0_fastreject_function reject, void *pass)
 {
-       d0_blind_id_clear(ctx);
-       CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_new());
-       CHECK(d0_dl_generate_key(k, ctx->schnorr_G));
-       CHECK_ASSIGN(ctx->rsa_e, d0_bignum_int(NULL, 65537));
-       CHECK_ASSIGN(ctx->rsa_d, d0_bignum_new());
-       CHECK_ASSIGN(ctx->rsa_n, d0_bignum_new());
-       CHECK(d0_rsa_generate_key(k+1, ctx->rsa_e, ctx->rsa_d, ctx->rsa_n)); // must fit G for sure
+       REPLACING(rsa_e); REPLACING(rsa_d); REPLACING(rsa_n);
+
+       CHECK_ASSIGN(ctx->rsa_e, d0_bignum_int(ctx->rsa_e, 65537));
+       CHECK_ASSIGN(ctx->rsa_d, d0_bignum_zero(ctx->rsa_d));
+       CHECK_ASSIGN(ctx->rsa_n, d0_bignum_zero(ctx->rsa_n));
+       if(reject)
+               CHECK(d0_rsa_generate_key_fastreject(k+1, reject, ctx, pass)); // must fit G for sure
+       else
+               CHECK(d0_rsa_generate_key(k+1, ctx->rsa_e, ctx->rsa_d, ctx->rsa_n)); // must fit G for sure
        return 1;
 fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_keys(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_key(d0_blind_id_t *ctx, int k)
 {
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
-       d0_blind_id_clear(ctx);
-       CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, NULL));
-       CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, NULL));
-       CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, NULL));
-       CHECK_ASSIGN(ctx->rsa_d, d0_iobuf_read_bignum(in, NULL));
+       return d0_blind_id_generate_private_key_fastreject(ctx, k, NULL, NULL);
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+{
+       d0_iobuf_t *in = NULL;
+
+       REPLACING(rsa_n); REPLACING(rsa_e); REPLACING(rsa_d);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+
+       CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
+       CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
+       CHECK_ASSIGN(ctx->rsa_d, d0_iobuf_read_bignum(in, ctx->rsa_d));
        return d0_iobuf_close(in, NULL);
 
 fail:
@@ -231,13 +403,15 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_keys(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_public_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
 {
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
-       d0_blind_id_clear(ctx);
-       CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, NULL));
-       CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, NULL));
-       CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, NULL));
+       d0_iobuf_t *in = NULL;
+
+       REPLACING(rsa_n); REPLACING(rsa_e);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+       CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
+       CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
        return d0_iobuf_close(in, NULL);
 
 fail:
@@ -245,16 +419,13 @@ fail:
        return 0;
 }
 
-#define USING(x) if(!(ctx->x)) return 0
-#define WRITING(x,f) if(ctx->x) { f(ctx->x); ctx->x = NULL; }
-#define REPLACING(x)
-
-WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_keys(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
+       d0_iobuf_t *out = NULL;
+
        USING(rsa_n); USING(rsa_e); USING(rsa_d);
 
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
-       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
        CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
        CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
        CHECK(d0_iobuf_write_bignum(out, ctx->rsa_d));
@@ -265,12 +436,13 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_keys(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_public_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
-       USING(rsa_n); USING(rsa_e); USING(rsa_d);
+       d0_iobuf_t *out = NULL;
 
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
-       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
+       USING(rsa_n); USING(rsa_e);
+
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
        CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
        CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
        return d0_iobuf_close(out, outbuflen);
@@ -281,32 +453,121 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_start(d0_blind_id_t *ctx)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_fingerprint64_public_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+{
+       d0_iobuf_t *out = NULL;
+       static unsigned char convbuf[2048];
+       d0_iobuf_t *conv = NULL;
+       size_t sz, n;
+
+       USING(rsa_n); USING(rsa_e);
+
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
+
+       CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_n));
+       CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_e));
+       CHECK(d0_iobuf_close(conv, &sz));
+       conv = NULL;
+
+       n = (*outbuflen / 4) * 3;
+       if(n > SHA_DIGESTSIZE)
+               n = SHA_DIGESTSIZE;
+       CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), n) == n);
+       CHECK(d0_iobuf_conv_base64_out(out));
+
+       return d0_iobuf_close(out, outbuflen);
+
+fail:
+       if(conv)
+               d0_iobuf_close(conv, &sz);
+       d0_iobuf_close(out, outbuflen);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_id_modulus(d0_blind_id_t *ctx)
+{
+       USING(rsa_n);
+       REPLACING(schnorr_G);
+
+       CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_zero(ctx->schnorr_G));
+       CHECK(d0_dl_generate_key(d0_bignum_size(ctx->rsa_n)-1, ctx->schnorr_G));
+       return 1;
+fail:
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_id_modulus(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+{
+       d0_iobuf_t *in = NULL;
+
+       REPLACING(schnorr_G);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+       CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
+       return d0_iobuf_close(in, NULL);
+
+fail:
+       d0_iobuf_close(in, NULL);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_id_modulus(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
-       // temps: temp0 order
+       d0_iobuf_t *out = NULL;
+
        USING(schnorr_G);
-       REPLACING(schnorr_s); REPLACING(schnorr_4_to_s);
+
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
+       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
+       return d0_iobuf_close(out, outbuflen);
+
+fail:
+       d0_iobuf_close(out, outbuflen);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_id_start(d0_blind_id_t *ctx)
+{
+       // temps: temp0 = order
+       USING(schnorr_G);
+       REPLACING(schnorr_s); REPLACING(schnorr_g_to_s);
 
        CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
        CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_rand_range(ctx->schnorr_s, zero, temp0));
-       CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mod_pow(ctx->schnorr_4_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
+       CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_bignum_mod_pow(ctx->schnorr_g_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
+       CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_bignum_zero(ctx->schnorr_H_g_to_s_signature));
        return 1;
 
 fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
-       // temps: temp0 temp1
-       USING(rsa_n); USING(rsa_e); USING(schnorr_4_to_s);
-       REPLACING(rn);
+       d0_iobuf_t *out = NULL;
+       static unsigned char shabuf[2048];
+       size_t sz;
+
+       // temps: temp0 rsa_blind_signature_camouflage^challenge, temp1 (4^s)*rsa_blind_signature_camouflage^challenge
+       USING(rsa_n); USING(rsa_e); USING(schnorr_g_to_s);
+       REPLACING(rsa_blind_signature_camouflage);
 
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
-       CHECK_ASSIGN(ctx->rn, d0_bignum_rand_bit_atmost(ctx->rn, d0_bignum_size(ctx->rsa_n)));
-       CHECK(d0_bignum_mod_pow(temp0, ctx->rn, ctx->rsa_e, ctx->rsa_n));
-       CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_4_to_s, temp0, ctx->rsa_n));
+       CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_bignum_rand_bit_atmost(ctx->rsa_blind_signature_camouflage, d0_bignum_size(ctx->rsa_n)));
+       CHECK(d0_bignum_mod_pow(temp0, ctx->rsa_blind_signature_camouflage, ctx->rsa_e, ctx->rsa_n));
+
+       // we will actually sign HA(4^s) to prevent a malleability attack!
+       CHECK(d0_bignum_mov(temp2, ctx->schnorr_g_to_s));
+       sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
+       if(sz > sizeof(shabuf))
+               sz = sizeof(shabuf);
+       CHECK(d0_longhash_bignum(temp2, shabuf, sz));
+       CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
+
+       // hash complete
+       CHECK(d0_bignum_mod_mul(temp1, temp2, temp0, ctx->rsa_n));
        CHECK(d0_iobuf_write_bignum(out, temp1));
        return d0_iobuf_close(out, outbuflen);
 
@@ -315,13 +576,16 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_answer_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_answer_private_id_request(const d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
 {
-       // temps: temp0 temp1
+       d0_iobuf_t *in = NULL;
+       d0_iobuf_t *out = NULL;
+
+       // temps: temp0 input, temp1 temp0^d
        USING(rsa_d); USING(rsa_n);
 
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
        CHECK(d0_iobuf_read_bignum(in, temp0));
        CHECK(d0_bignum_mod_pow(temp1, temp0, ctx->rsa_d, ctx->rsa_n));
@@ -336,17 +600,36 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_finish_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_finish_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
 {
-       // temps: temp0 temp1
-       USING(rn); USING(rsa_n);
-       REPLACING(schnorr_4_to_s_signature);
+       d0_iobuf_t *in = NULL;
 
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
+       // temps: temp0 input, temp1 rsa_blind_signature_camouflage^-1
+       USING(rsa_blind_signature_camouflage); USING(rsa_n);
+       REPLACING(schnorr_H_g_to_s_signature);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
 
        CHECK(d0_iobuf_read_bignum(in, temp0));
-       CHECK(d0_bignum_mod_inv(temp1, ctx->rn, ctx->rsa_n));
-       CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_4_to_s_signature, temp0, temp1, ctx->rsa_n));
+       CHECK(d0_bignum_mod_inv(temp1, ctx->rsa_blind_signature_camouflage, ctx->rsa_n));
+       CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_H_g_to_s_signature, temp0, temp1, ctx->rsa_n));
+
+       return d0_iobuf_close(in, NULL);
+
+fail:
+       d0_iobuf_close(in, NULL);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_id_request_camouflage(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+{
+       d0_iobuf_t *in = NULL;
+
+       REPLACING(rsa_blind_signature_camouflage);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+
+       CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_iobuf_read_bignum(in, ctx->rsa_blind_signature_camouflage));
 
        return d0_iobuf_close(in, NULL);
 
@@ -355,15 +638,34 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_read_private_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_id_request_camouflage(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
-       REPLACING(schnorr_s); REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
+       d0_iobuf_t *out = NULL;
+
+       USING(rsa_blind_signature_camouflage);
+
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
+       CHECK(d0_iobuf_write_bignum(out, ctx->rsa_blind_signature_camouflage));
+
+       return d0_iobuf_close(out, outbuflen);
+
+fail:
+       d0_iobuf_close(out, outbuflen);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+{
+       d0_iobuf_t *in = NULL;
+
+       REPLACING(schnorr_s); REPLACING(schnorr_g_to_s); REPLACING(schnorr_H_g_to_s_signature);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
 
        CHECK_ASSIGN(ctx->schnorr_s, d0_iobuf_read_bignum(in, ctx->schnorr_s));
-       CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
-       CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
+       CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_g_to_s));
+       CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_g_to_s_signature));
 
        return d0_iobuf_close(in, NULL);
 
@@ -372,14 +674,16 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_read_public_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_public_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
 {
-       REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
+       d0_iobuf_t *in = NULL;
+
+       REPLACING(schnorr_g_to_s); REPLACING(schnorr_H_g_to_s_signature);
 
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
+       in = d0_iobuf_open_read(inbuf, inbuflen);
 
-       CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
-       CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
+       CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_g_to_s));
+       CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_g_to_s_signature));
 
        return d0_iobuf_close(in, NULL);
 
@@ -388,15 +692,17 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_write_private_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
-       USING(schnorr_s); USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
+       d0_iobuf_t *out = NULL;
 
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
+       USING(schnorr_s); USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
+
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
        CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_s));
-       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
-       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
+       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_g_to_s));
+       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_g_to_s_signature));
 
        return d0_iobuf_close(out, outbuflen);
 
@@ -405,14 +711,16 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_write_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
-       USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
+       d0_iobuf_t *out = NULL;
+
+       USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
 
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
-       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
-       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
+       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_g_to_s));
+       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_g_to_s_signature));
 
        return d0_iobuf_close(out, outbuflen);
 
@@ -421,40 +729,58 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_start(d0_blind_id_t *ctx, int is_first, char *msg, size_t msglen, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_start(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL send_modulus, const char *msg, size_t msglen, char *outbuf, size_t *outbuflen)
 // start =
 //   first run: send 4^s, 4^s signature
 //   1. get random r, send HASH(4^r)
 {
+       d0_iobuf_t *out = NULL;
+       static unsigned char convbuf[1024];
+       d0_iobuf_t *conv = NULL;
+       size_t sz = 0;
+       D0_BOOL failed = 0;
+
+       // temps: temp0 order, temp0 4^r
        if(is_first)
        {
-               USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
+               USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
        }
        USING(schnorr_G);
-       REPLACING(r);
+       REPLACING(r); REPLACING(t); REPLACING(g_to_t);
 
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
        if(is_first)
        {
                // send ID
-               CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
-               CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
+               if(send_modulus)
+                       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
+               CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_g_to_s));
+               CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_g_to_s_signature));
        }
 
        // start schnorr ID scheme
        // generate random number r; x = g^r; send hash of x, remember r, forget x
        CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
        CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
+       //CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
+
+       // initialize Signed Diffie Hellmann
+       // we already have the group order in temp1
+       CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
+       // can we SOMEHOW do this with just one mod_pow?
+
        CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
+       CHECK_ASSIGN(ctx->g_to_t, d0_bignum_mod_pow(ctx->g_to_t, four, ctx->t, ctx->schnorr_G));
+       CHECK(!failed);
 
        // hash it, hash it, everybody hash it
-       unsigned char convbuf[1024];
-       d0_iobuf_t *conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
-       size_t sz;
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
        CHECK(d0_iobuf_write_bignum(conv, temp0));
+       CHECK(d0_iobuf_write_bignum(conv, ctx->g_to_t));
        CHECK(d0_iobuf_write_packet(conv, msg, msglen));
        CHECK(d0_iobuf_write_bignum(conv, temp0));
+       CHECK(d0_iobuf_write_bignum(conv, ctx->g_to_t));
        d0_iobuf_close(conv, &sz);
        conv = NULL;
        CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), SCHNORR_HASHSIZE) == SCHNORR_HASHSIZE);
@@ -467,54 +793,90 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_challenge(d0_blind_id_t *ctx, int is_first, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_challenge(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL recv_modulus, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen, D0_BOOL *status)
 //   first run: get 4^s, 4^s signature
 //   1. check sig
 //   2. save HASH(4^r)
-//   3. send challenge e of SCHNORR_BITS
+//   3. send challenge challenge of SCHNORR_BITS
 {
+       d0_iobuf_t *in = NULL;
+       d0_iobuf_t *out = NULL;
+       static unsigned char shabuf[2048];
+       size_t sz;
+
+       // temps: temp0 order, temp0 signature check
        if(is_first)
        {
-               REPLACING(schnorr_4_to_s); REPLACING(k); REPLACING(schnorr_4_to_s_signature);
-               USING(schnorr_G); USING(rsa_n);
+               REPLACING(schnorr_g_to_s); REPLACING(schnorr_H_g_to_s_signature);
+               if(recv_modulus)
+                       REPLACING(schnorr_G);
+               else
+                       USING(schnorr_G);
        }
        else
        {
-               USING(schnorr_4_to_s_signature); USING(schnorr_4_to_s);
+               USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
+               USING(schnorr_G);
        }
        USING(rsa_e); USING(rsa_n);
-       REPLACING(e); REPLACING(msg); REPLACING(msglen);
+       REPLACING(challenge); REPLACING(msg); REPLACING(msglen); REPLACING(msghash); REPLACING(r); REPLACING(t);
 
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
        if(is_first)
        {
-               CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, NULL));
-               CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, zero) >= 0);
-               CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, ctx->schnorr_G) < 0);
-               CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
-               CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero) >= 0);
-               CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, ctx->rsa_n) < 0);
-       }
-
-       // check signature of key (t = k^d, so, t^e = k)
-       CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_4_to_s_signature, ctx->rsa_e, ctx->rsa_n));
-       if(d0_bignum_cmp(temp0, ctx->schnorr_4_to_s))
-       {
-               // FAIL (not signed by Xonotic)
-               goto fail;
-               // TODO: accept the key anyway, but mark as failed signature!
+               if(recv_modulus)
+               {
+                       CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
+                       CHECK(d0_bignum_cmp(ctx->schnorr_G, zero) > 0);
+                       CHECK(d0_bignum_cmp(ctx->schnorr_G, ctx->rsa_n) < 0);
+               }
+               CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_g_to_s));
+               CHECK(d0_bignum_cmp(ctx->schnorr_g_to_s, zero) >= 0);
+               CHECK(d0_bignum_cmp(ctx->schnorr_g_to_s, ctx->schnorr_G) < 0);
+               CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_g_to_s_signature));
+               CHECK(d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero) >= 0);
+               CHECK(d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, ctx->rsa_n) < 0);
+
+               // check signature of key (t = k^d, so, t^challenge = k)
+               CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_H_g_to_s_signature, ctx->rsa_e, ctx->rsa_n));
+
+               // we will actually sign SHA(4^s) to prevent a malleability attack!
+               CHECK(d0_bignum_mov(temp2, ctx->schnorr_g_to_s));
+               sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
+               if(sz > sizeof(shabuf))
+                       sz = sizeof(shabuf);
+               CHECK(d0_longhash_bignum(temp2, shabuf, sz));
+               CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
+
+               // + 7 / 8 is too large, so let's mod it
+               CHECK(d0_bignum_divmod(NULL, temp1, temp2, ctx->rsa_n));
+
+               // hash complete
+               if(d0_bignum_cmp(temp0, temp1))
+               {
+                       // accept the key anyway, but mark as failed signature! will later return 0 in status
+                       CHECK(d0_bignum_zero(ctx->schnorr_H_g_to_s_signature));
+               }
        }
 
-       CHECK(d0_iobuf_read_raw(in, ctx->xnbh, SCHNORR_HASHSIZE));
+       CHECK(d0_iobuf_read_raw(in, ctx->msghash, SCHNORR_HASHSIZE));
        ctx->msglen = MSGSIZE;
        CHECK(d0_iobuf_read_packet(in, ctx->msg, &ctx->msglen));
 
        // send challenge
-       CHECK_ASSIGN(ctx->e, d0_bignum_rand_bit_atmost(ctx->e, SCHNORR_BITS));
+       CHECK_ASSIGN(ctx->challenge, d0_bignum_rand_bit_atmost(ctx->challenge, SCHNORR_BITS));
+       CHECK(d0_iobuf_write_bignum(out, ctx->challenge));
 
-       CHECK(d0_iobuf_write_bignum(out, ctx->e));
+       // Diffie Hellmann send
+       CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
+       CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
+       CHECK(d0_bignum_mod_pow(temp0, four, ctx->t, ctx->schnorr_G));
+       CHECK(d0_iobuf_write_bignum(out, temp0));
+
+       if(status)
+               *status = !!d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero);
 
        d0_iobuf_close(in, NULL);
        return d0_iobuf_close(out, outbuflen);
@@ -525,28 +887,38 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_response(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
-//   1. read challenge e of SCHNORR_BITS
-//   2. reply with r + s * e mod order
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_response(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
+//   1. read challenge challenge of SCHNORR_BITS
+//   2. reply with r + s * challenge mod order
 {
-       // temps: 0 order, 1 prod, 2 y, 3 e
-       USING(schnorr_G); USING(schnorr_s); USING(r);
+       d0_iobuf_t *in = NULL;
+       d0_iobuf_t *out = NULL;
+
+       // temps: 0 order, 1 prod, 2 y, 3 challenge
+       REPLACING(other_g_to_t); REPLACING(t);
+       USING(schnorr_G); USING(schnorr_s); USING(r); USING(g_to_t);
 
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
        CHECK(d0_iobuf_read_bignum(in, temp3));
-       // TODO check if >= 2^SCHNORR_BITS or < 0, if yes, then fail (needed for zero knowledge)
        CHECK(d0_bignum_cmp(temp3, zero) >= 0);
        CHECK(d0_bignum_size(temp3) <= SCHNORR_BITS);
 
        // send response for schnorr ID scheme
-       // i.e. r + ctx->schnorr_s * temp3
+       // i.challenge. r + ctx->schnorr_s * temp3
        CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
        CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_s, temp3, temp0));
        CHECK(d0_bignum_mod_add(temp2, temp1, ctx->r, temp0));
        CHECK(d0_iobuf_write_bignum(out, temp2));
 
+       // Diffie Hellmann recv
+       CHECK_ASSIGN(ctx->other_g_to_t, d0_iobuf_read_bignum(in, ctx->other_g_to_t));
+       CHECK(d0_bignum_cmp(ctx->other_g_to_t, zero) > 0);
+       CHECK(d0_bignum_cmp(ctx->other_g_to_t, ctx->schnorr_G) < 0);
+       // Diffie Hellmann send
+       CHECK(d0_iobuf_write_bignum(out, ctx->g_to_t));
+
        d0_iobuf_close(in, NULL);
        return d0_iobuf_close(out, outbuflen);
 
@@ -556,46 +928,58 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_authenticate_with_private_id_verify(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *msg, ssize_t *msglen)
-//   1. read y = r + s * e mod order
-//   2. verify: g^y (g^s)^-e = g^(r+s*e-s*e) = g^r
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_verify(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *msg, size_t *msglen, D0_BOOL *status)
+//   1. read y = r + s * challenge mod order
+//   2. verify: g^y (g^s)^-challenge = g^(r+s*challenge-s*challenge) = g^r
 //      (check using H(g^r) which we know)
 {
+       d0_iobuf_t *in = NULL;
+       static unsigned char convbuf[1024];
+       d0_iobuf_t *conv = NULL;
+       size_t sz;
+
        // temps: 0 y 1 order
-       USING(e); USING(schnorr_G);
+       USING(challenge); USING(schnorr_G);
+       REPLACING(other_g_to_t);
 
-       d0_iobuf_t *in = d0_iobuf_open_read(inbuf, inbuflen);
+       in = d0_iobuf_open_read(inbuf, inbuflen);
 
-       *msglen = -1;
        CHECK(d0_dl_get_order(temp1, ctx->schnorr_G));
        CHECK(d0_iobuf_read_bignum(in, temp0));
        CHECK(d0_bignum_cmp(temp0, zero) >= 0);
        CHECK(d0_bignum_cmp(temp0, temp1) < 0);
 
        // verify schnorr ID scheme
-       // we need 4^temp0 (g^s)^-e
-       CHECK(d0_bignum_neg(temp1, ctx->e));
-       CHECK(d0_bignum_mod_pow(temp2, ctx->schnorr_4_to_s, temp1, ctx->schnorr_G));
+       // we need 4^r = 4^temp0 (g^s)^-challenge
+       CHECK(d0_bignum_mod_inv(temp1, ctx->schnorr_g_to_s, ctx->schnorr_G));
+       CHECK(d0_bignum_mod_pow(temp2, temp1, ctx->challenge, ctx->schnorr_G));
        CHECK(d0_bignum_mod_pow(temp1, four, temp0, ctx->schnorr_G));
-       CHECK(d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G));
-       // hash must be equal to xnbh
+       CHECK_ASSIGN(temp3, d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G));
+
+       // Diffie Hellmann recv
+       CHECK_ASSIGN(ctx->other_g_to_t, d0_iobuf_read_bignum(in, ctx->other_g_to_t));
+       CHECK(d0_bignum_cmp(ctx->other_g_to_t, zero) > 0);
+       CHECK(d0_bignum_cmp(ctx->other_g_to_t, ctx->schnorr_G) < 0);
 
        // hash it, hash it, everybody hash it
-       unsigned char convbuf[1024];
-       d0_iobuf_t *conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
-       size_t sz;
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
        CHECK(d0_iobuf_write_bignum(conv, temp3));
+       CHECK(d0_iobuf_write_bignum(conv, ctx->other_g_to_t));
        CHECK(d0_iobuf_write_packet(conv, ctx->msg, ctx->msglen));
        CHECK(d0_iobuf_write_bignum(conv, temp3));
+       CHECK(d0_iobuf_write_bignum(conv, ctx->other_g_to_t));
        d0_iobuf_close(conv, &sz);
        conv = NULL;
-       if(memcmp(sha(convbuf, sz), ctx->xnbh, SCHNORR_HASHSIZE))
+       if(memcmp(sha(convbuf, sz), ctx->msghash, SCHNORR_HASHSIZE))
        {
                // FAIL (not owned by player)
                goto fail;
        }
 
-       if(ctx->msglen <= (size_t) *msglen)
+       if(status)
+               *status = !!d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero);
+
+       if(ctx->msglen <= *msglen)
                memcpy(msg, ctx->msg, ctx->msglen);
        else
                memcpy(msg, ctx->msg, *msglen);
@@ -609,39 +993,235 @@ fail:
        return 0;
 }
 
-WARN_UNUSED_RESULT BOOL d0_blind_id_fingerprint64_public_id(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_generate_missing_signature(d0_blind_id_t *ctx)
 {
-       USING(schnorr_4_to_s);
+       size_t sz;
+       static unsigned char shabuf[2048];
+
+       REPLACING(schnorr_H_g_to_s_signature);
+       USING(schnorr_g_to_s); USING(rsa_d); USING(rsa_n);
+
+       // we will actually sign SHA(4^s) to prevent a malleability attack!
+       CHECK(d0_bignum_mov(temp2, ctx->schnorr_g_to_s));
+       sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
+       if(sz > sizeof(shabuf))
+               sz = sizeof(shabuf);
+       CHECK(d0_longhash_bignum(temp2, shabuf, sz));
+       CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
+
+       // + 7 / 8 is too large, so let's mod it
+       CHECK(d0_bignum_divmod(NULL, temp1, temp2, ctx->rsa_n));
+       CHECK(d0_bignum_mod_pow(ctx->schnorr_H_g_to_s_signature, temp1, ctx->rsa_d, ctx->rsa_n));
+       return 1;
+
+fail:
+       return 0;
+}
 
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_sign_with_private_id_sign(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL send_modulus, const char *message, size_t msglen, char *outbuf, size_t *outbuflen)
+{
+       d0_iobuf_t *out = NULL;
        static unsigned char convbuf[1024];
-       d0_iobuf_t *out = d0_iobuf_open_write(outbuf, *outbuflen);
-       d0_iobuf_t *conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
+       static unsigned char shabuf[1024];
+       d0_iobuf_t *conv = NULL;
+       size_t sz = 0;
 
-       size_t n, sz;
+       if(is_first)
+       {
+               USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
+       }
+       USING(schnorr_G);
+       USING(schnorr_s);
+       REPLACING(r);
+
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
 
-       CHECK(d0_iobuf_write_bignum(conv, ctx->schnorr_4_to_s));
+       if(is_first)
+       {
+               // send ID
+               if(send_modulus)
+                       CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
+               CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_g_to_s));
+               CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_g_to_s_signature));
+       }
+
+       // start schnorr SIGNATURE scheme
+       // generate random number r; x = g^r; send hash of H(m||r), remember r, forget x
+       CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
+       CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
+       CHECK(d0_bignum_mod_pow(temp1, four, ctx->r, ctx->schnorr_G));
+
+       // hash it, hash it, everybody hash it
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
+       CHECK(d0_iobuf_write_packet(conv, message, msglen));
+       CHECK(d0_iobuf_write_bignum(conv, temp1));
+       d0_iobuf_close(conv, &sz);
+       conv = NULL;
+       CHECK(d0_longhash_destructive(convbuf, sz, shabuf, (d0_bignum_size(temp0) + 7) / 8));
+       CHECK(d0_bignum_import_unsigned(temp2, shabuf, (d0_bignum_size(temp0) + 7) / 8));
+       CHECK(d0_iobuf_write_bignum(out, temp2));
+
+       // multiply with secret, sub k, modulo order
+       CHECK(d0_bignum_mod_mul(temp1, temp2, ctx->schnorr_s, temp0));
+       CHECK(d0_bignum_mod_sub(temp2, ctx->r, temp1, temp0));
+       CHECK(d0_iobuf_write_bignum(out, temp2));
+
+       // write the message itself
+       CHECK(d0_iobuf_write_packet(out, message, msglen));
+
+       return d0_iobuf_close(out, outbuflen);
+
+fail:
+       d0_iobuf_close(out, outbuflen);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_sign_with_private_id_verify(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL recv_modulus, const char *inbuf, size_t inbuflen, char *msg, size_t *msglen, D0_BOOL *status)
+{
+       d0_iobuf_t *in = NULL;
+       d0_iobuf_t *conv = NULL;
+       static unsigned char convbuf[2048];
+       static unsigned char shabuf[2048];
+       size_t sz;
+
+       if(is_first)
+       {
+               REPLACING(schnorr_g_to_s); REPLACING(schnorr_H_g_to_s_signature);
+               if(recv_modulus)
+                       REPLACING(schnorr_G);
+               else
+                       USING(schnorr_G);
+       }
+       else
+       {
+               USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
+               USING(schnorr_G);
+       }
+       USING(rsa_e); USING(rsa_n);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+
+       if(is_first)
+       {
+               if(recv_modulus)
+               {
+                       CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
+                       CHECK(d0_bignum_cmp(ctx->schnorr_G, zero) > 0);
+                       CHECK(d0_bignum_cmp(ctx->schnorr_G, ctx->rsa_n) < 0);
+               }
+               CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_g_to_s));
+               CHECK(d0_bignum_cmp(ctx->schnorr_g_to_s, zero) >= 0);
+               CHECK(d0_bignum_cmp(ctx->schnorr_g_to_s, ctx->schnorr_G) < 0);
+               CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_g_to_s_signature));
+               CHECK(d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero) >= 0);
+               CHECK(d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, ctx->rsa_n) < 0);
+
+               // check signature of key (t = k^d, so, t^challenge = k)
+               CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_H_g_to_s_signature, ctx->rsa_e, ctx->rsa_n));
+
+               // we will actually sign SHA(4^s) to prevent a malleability attack!
+               CHECK(d0_bignum_mov(temp2, ctx->schnorr_g_to_s));
+               sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
+               if(sz > sizeof(shabuf))
+                       sz = sizeof(shabuf);
+               CHECK(d0_longhash_bignum(temp2, shabuf, sz));
+               CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
+
+               // + 7 / 8 is too large, so let's mod it
+               CHECK(d0_bignum_divmod(NULL, temp1, temp2, ctx->rsa_n));
+
+               // hash complete
+               if(d0_bignum_cmp(temp0, temp1))
+               {
+                       // accept the key anyway, but mark as failed signature! will later return 0 in status
+                       CHECK(d0_bignum_zero(ctx->schnorr_H_g_to_s_signature));
+               }
+       }
+
+       CHECK(d0_dl_get_order(temp4, ctx->schnorr_G));
+       CHECK(d0_iobuf_read_bignum(in, temp0)); // e == H(m || g^r)
+       CHECK(d0_iobuf_read_bignum(in, temp1)); // x == (r - s*e) mod |G|
+       CHECK(d0_iobuf_read_packet(in, msg, msglen));
+
+       // VERIFY: g^x * (g^s)^-e = g^(x - s*e) = g^r
+
+       // verify schnorr ID scheme
+       // we need g^r = g^x (g^s)^e
+       CHECK(d0_bignum_mod_pow(temp2, four, temp1, ctx->schnorr_G));
+       CHECK(d0_bignum_mod_pow(temp1, ctx->schnorr_g_to_s, temp0, ctx->schnorr_G));
+       CHECK_ASSIGN(temp3, d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G)); // temp3 now is g^r
+
+       // hash it, hash it, everybody hash it
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
+       CHECK(d0_iobuf_write_packet(conv, msg, *msglen));
+       CHECK(d0_iobuf_write_bignum(conv, temp3));
+       d0_iobuf_close(conv, &sz);
+       conv = NULL;
+       CHECK(d0_longhash_destructive(convbuf, sz, shabuf, (d0_bignum_size(temp4) + 7) / 8));
+       CHECK(d0_bignum_import_unsigned(temp1, shabuf, (d0_bignum_size(temp4) + 7) / 8));
+
+       // verify signature
+       CHECK(!d0_bignum_cmp(temp0, temp1));
+
+       if(status)
+               *status = !!d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero);
+
+       d0_iobuf_close(in, NULL);
+       return 1;
+
+fail:
+       d0_iobuf_close(in, NULL);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_fingerprint64_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+{
+       d0_iobuf_t *out = NULL;
+       static unsigned char convbuf[1024];
+       d0_iobuf_t *conv = NULL;
+       size_t sz, n;
+
+       USING(rsa_n);
+       USING(rsa_e);
+       USING(schnorr_g_to_s);
+
+       out = d0_iobuf_open_write(outbuf, *outbuflen);
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
+
+       CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_n));
+       CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_e));
+       CHECK(d0_iobuf_write_bignum(conv, ctx->schnorr_g_to_s));
        CHECK(d0_iobuf_close(conv, &sz));
        conv = NULL;
 
        n = (*outbuflen / 4) * 3;
        if(n > SHA_DIGESTSIZE)
                n = SHA_DIGESTSIZE;
-       if(d0_iobuf_write_raw(out, sha(convbuf, sz), n) != n)
-               goto fail;
-       if(!d0_iobuf_conv_base64_out(out))
-               goto fail;
+       CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), n) == n);
+       CHECK(d0_iobuf_conv_base64_out(out));
 
        return d0_iobuf_close(out, outbuflen);
 
 fail:
        if(conv)
-               if(!d0_iobuf_close(conv, &sz)) { }
-       if(!d0_iobuf_close(out, outbuflen))
-               return 0;
+               d0_iobuf_close(conv, &sz);
+       d0_iobuf_close(out, outbuflen);
        return 0;
 }
 
-d0_blind_id_t *d0_blind_id_new()
+D0_BOOL d0_blind_id_sessionkey_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
+{
+       USING(t); USING(other_g_to_t); USING(schnorr_G);
+
+       // temps: temp0 result
+       CHECK(d0_bignum_mod_pow(temp0, ctx->other_g_to_t, ctx->t, ctx->schnorr_G));
+       return d0_longhash_bignum(temp0, (unsigned char *) outbuf, *outbuflen);
+
+fail:
+       return 0;
+}
+
+d0_blind_id_t *d0_blind_id_new(void)
 {
        d0_blind_id_t *b = d0_malloc(sizeof(d0_blind_id_t));
        memset(b, 0, sizeof(*b));
@@ -653,3 +1233,11 @@ void d0_blind_id_free(d0_blind_id_t *a)
        d0_blind_id_clear(a);
        d0_free(a);
 }
+
+void d0_blind_id_util_sha256(char *out, const char *in, size_t n)
+{
+       SHA256_CTX context;
+       SHA256_Init(&context);
+       SHA256_Update(&context, (const unsigned char *) in, n);
+       return SHA256_Final((unsigned char *) out, &context);
+}