[OTR-dev] [OTR-users] otr dh key encryption

[Michael Rogers]

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On 19/02/13 18:13, Ileana wrote:
>> Neither torchat nor OTR use 256 bit AES, they both use 128 bit
>> AES.
> 
> OK...this part I am pretty sure is a mistake.  Tor purports to use 
> AES-256 for all connections, including hidden services...I relooked
> at the OTR code and see the that 16 bytes * 8 bits is indeed 128.

According to the spec, Tor uses 128-bit AES.

https://gitweb.torproject.org/torspec.git?a=blob_plain;hb=HEAD;f=tor-spec.txt

"For a stream cipher, we use 128-bit AES in counter mode, with an IV
of all 0 bytes."

Another potential concern is that the hostname of a hidden service is
based on the first 80 bits of the hash of the service's public key, so
a collision can be generated after an expected 2^80 attempts.

https://gitweb.torproject.org/torspec.git?a=blob_plain;hb=HEAD;f=rend-spec.txt
(see section 1.5)

Cheers,
Michael

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