Interoperability with OpenSSH3.4p1 and OpenSSH4.3p2


I am working on an SSH implementation that has to
connect to a SSH
server. I find that the length of the DH modulus
contained in
SSH2_MSG_KEX_DH_GEX_GROUP (as defined by RFC 4419)
message sent by
the server for a 2048-bit DH key scenario is 399 bytes
as opposed to
256 bytes. This is causing trouble with the client as
the length is
uncharacteristic of the known DH group 14 .

However for a scenario of a 1024-bit key, as expected
a 128 byte
modulus is sent by the server in the

Could some one explain this deviation from standard?
Am i missing the
math involved in the size of the modulus that is sent

Please clarify,

Yahoo! India Answers: Share what you know. Learn something new