[Cryptography Team] Reading ssh pub/private keys

[Bert Freudenberg]

Hi Rob,

turns out the private key file has the public part in it, too, it  
stores (0, p, q, g, y, x). DSAPrivateKeyFileReader assumes some more  
fields whereas my key just has the blob data in it, and it is not  
encrypted by a passphrase. Using the ASN.1 reader on my blob worked  
fine, though.

Thanks a lot!

- Bert -

On Mar 29, 2007, at 15:33 , Robert Withers wrote:

> Bert, there are indeed Base64 encoded.  For starters, you can try:
>
> 	(DSAPrivateKeyFileReader fromFile: privateKeyFileName) asPrivateKey
>
> I am not sure about the publicKey, but you could try the same  
> reader code.  Internally, it strips off the PEM markings (----- 
> BEGIN DSA...and so on), the does a Base64 decode and leaves you  
> with bytes.  The #asPrivateKey will take those bytes and do an ASN. 
> 1 decode on them.  My point is that the PublicKey may also be ASN.1  
> encoded, so you may find some traction here.
>
> Let me know how it goes.
>
> Are you implementing SSH?!
>
> cheers,
> Robert
>
> On Mar 29, 2007, at 6:23 AM, Bert Freudenberg wrote:
>
>> Hi folks,
>>
>> I have an ssh-format keypair and would like to extract the  
>> (p,q,g,x) and (p,q,g,y) DSA tuples from that. The private key  
>> looks like this:
>>
>> -----BEGIN DSA PRIVATE KEY-----
>> MIIBuwIB..............XCIa3cIp
>> -----END DSA PRIVATE KEY-----
>>
>> and the public key:
>>
>> ssh-dss AAAAB3NzaC1k.........nNEnWCasjXraVA==
>>
>> So this looks like Base64-encoded numbers, but how are they  
>> encoded? The only reference I found was this:
>>
>> http://www.openssh.com/txt/draft-ietf-secsh-publickeyfile-02.txt
>>
>> But it does not detail how the "binary blob" translates to DSA  
>> tuples.
>>
>> - Bert -
>>
>>
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