commit 94d3fe9a0802e2614d4a4b9297ed57b1979865fc Author: Yawning Angel yawning@torproject.org Date: Wed Aug 27 12:26:09 2014 +0000

Change the TYPE_PRNG_SEED length to 24.

This matches what the code actually sends. It's shorter than the ScrambleSuit PRNG seed, but that's because the SipHash-2-4 based Hash_DRBG has 24 bytes of internal state (key + initial output). --- doc/obfs4-spec.txt | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/doc/obfs4-spec.txt b/doc/obfs4-spec.txt index d2aa859..0e844a1 100644 --- a/doc/obfs4-spec.txt +++ b/doc/obfs4-spec.txt @@ -104,7 +104,7 @@

Length of the ntor AUTH tag (A HMAC-SHA256 digest).

- InlineSeedFrameLength = 53 + InlineSeedFrameLength = 45

Length of a unpadded TYPE_PRNG_SEED frame.

@@ -144,7 +144,7 @@

The amount of padding is chosen such that the smallest possible request and response (requests and responses with the minimum amount of padding) are - equal in size. For details on the InlineSeedFrameLength, see section 7. + equal in size. For details on the InlineSeedFrameLength, see section 6.

The client handshake process is as follows.

@@ -282,7 +282,7 @@ TYPE_PRNG_SEED (0x01):

The entire payload is to be treated as seeding material for the - protocol polymorphism PRNG. The format is 32 bytes of seeding + protocol polymorphism PRNG. The format is 24 bytes of seeding material.

Implementations SHOULD ignore unknown packet types for the purposes of