Merge branch 'master' of ssh://push.git.xonotic.org/d0_blind_id

[xonotic/d0_blind_id.git] / d0_blind_id.txt

diff --git a/d0_blind_id.txt b/d0_blind_id.txt
index 5b7db0765fb45d7c75eeeb93e656aaad7335d739..deb008aaab9a953b34b7a09abfe595238fa7b8d0 100644 (file)
--- a/d0_blind_id.txt
+++ b/d0_blind_id.txt
@@ -61,26 +61,28 @@ Authentication protocol:
        "start":
        - Client sends S, H if this is the first round of the protocol
        - Client generates r in [0, |G|[ at random
-       - Client sends x = h("g^r || m || g^r")
+       - Client generates t in [0, |G|[ at random
+       - Client sends x = h("g^r || g^t || m || g^r || g^t")
        - Client sends m in plain
        "challenge":
        - Server receives S, H if this is the first round of the protocol
        - Server verifies H = h'(I(S))
        - Server receives x, m
        - Server generates c in [0, 2^k0[ at random
-       - Server generates R in [0, |G|[ at random
-       - Server sends c and g^R
+       - Server generates T in [0, |G|[ at random
+       - Server sends c and g^T
        "response":
-       - Client receives c and g^R
+       - Client receives c and g^T
        - Client verifies that the received values are in the allowed ranges
-       - Client sends y = r + s * c mod |G|
-       - Client calculates K = (g^R)^r
+       - Client sends y = r - s * c mod |G|
+       - Client sends g^t
+       - Client calculates K = (g^T)^t
        "verify":
-       - Server receives y
-       - Server calculates z = g^y S^-c
-       - Server calculates x' = h("z || m || z")
+       - Server receives y and g^t
+       - Server calculates z = g^y S^c
+       - Server calculates x' = h("z || g^t || m || z || g^t")
        - Server verifies x == x'
-       - Server calculates K = z^R
+       - Server calculates K = (g^t)^T
 
 Protocol variant: g and G can be also part of the public ID. In this case, g
 and G are sent as part of this protocol additionally to S, H.
@@ -91,6 +93,20 @@ the same values on both sides only if the Schnorr identification scheme
 succeeds. If the protocol succeeds, the authenticity of m has been verified
 too.
 
+Signature protocol:
+       Client provides a message m that is to be signed as part of the protocol
+       "start":
+       - Client sends S, H if this is the first round of the protocol
+       - Client generates r in [0, |G|[ at random
+       - Client sends c = h("m || g^r")
+       - Client sends y = r - s * c
+       - Client sends m in plain
+       "verify":
+       - Server receives c, y, and m
+       - Server calculates z = g^y S^c
+       - Server calculates c' = h("m || z")
+       - Server verifies c == c'
+
 
 
 Low level protocol:
@@ -111,3 +127,31 @@ Low level protocol:
          "packet"
        - a value in double quotes is also defined in terms of this protocol, i.e.
          the length is preceded
+
+
+
+NOTE: to generate NON blind IDs, the process is not very straightforward. It
+works like this:
+
+Server shall:
+- load private key
+
+Both shall:
+- perform authentication as usual
+
+Server shall:
+- notice that the status is false
+- call d0_blind_id_authenticate_with_private_id_generate_missing_signature
+- write public ID
+- send that data to client
+
+Client shall:
+- read own private ID
+- get fingerprint
+- read received public ID (leaves the private part alone)
+- verify fingerprint
+- possibly verify ID
+- write own private ID again
+
+This ensures that only the ID the client authenticated with is signed by the
+server