See this link http://tools.ietf.org/html/rfc4253#page-15
Per the link, DSA signature is encoded as follows: string "ssh-dss" string dss_signature_blob RSA signature is encoded as follows: string "ssh-rsa" string rsa_signature_blob On Mon, Jul 8, 2013 at 8:48 AM, Kalpesh Parekh <[email protected]>wrote: > First, apologies for not replying inline to the emails. > > After your suggestions Alex, here is what I could determine. > > I printed out the hex code for the session key for both RSA and DSA types > in my setup. > > Here are the first few bytes: > (RSA) 00 00 00 07 73 73 68 2D 72 73 61 00 00 00 01 23 00 00 00 81 > > (DSA) 00 00 00 07 73 73 68 2D 64 73 73 00 00 00 81 > > As you mentioned, the first four bytes indicate, the length of the > identifier (7 in this case) > 73 73 68 2D 72 73 61=ssh-rsa > 73 73 68 2D 64 73 73=ssh-dsa > > The next four bytes for RSA indicates some sort of value. In my case it is > #. For DSA, it indicates (length of the key + 1) verified through > ssh-keygen -l command. > For RSA, the last four bytes printed above indicate (length of the key + > 1). > > > > > My next target is to decode the signature blobs. I feel like I am close > and can close this if any one can help. > > > > > > > > > On Thu, Jul 4, 2013 at 3:07 AM, Kalpesh Parekh <[email protected]>wrote: > >> Thanks Alex, >> >> So far it has been helpful. >> >> So based on the RFC, I understand that the host key received from the >> server has following components >> K_S || f || s >> >> I need to parse the K_S part for RSA key. How do I do that. >> >> Also, how can I implement a generic logic for getting the bit strength >> from the host key. >> >> > >
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