When I generate a DSA key with ssh-keygen -t dsa, the resulting public key will begin with ssh-dss.

How come? Why not ssh-dsa?

up vote 18 down vote accepted

DSS is simply a document that describes the signing procedure and specifies certain standards. The original document is FIPS 186 and latest revision in 2013 is FIPS 186-4. DSS is a standard for digital signing.

DSA is a cryptographic algorithm that generates keys, signs data, and verifies signatures. DSA, in itself, can use any hash function for its internal "cryptomagic", and it can also use any (L, N) for its parameters' length. DSS, as a standard, defines DSA's optional specifications.

DSS says that DSA should use SHA-1 as its hash function (recently, SHA-2). DSS says that DSA should use specific length pairs such as (2048,224), (3072,256), etc.

When SSH says DSS, they mean that they're implementing DSA in compliance with the DSS.

Cheap, one-sentence answer:

The Digital Signature Algorithm (DSA) is published in the Digital Signature Standard (DSS) by the NIST in FIPS 186.

The SSH version 2 standards apparently preferred "DSS", though more recently they've used "DSA" as well.

I don't know what the differences are in the definitions of the two terms, which is more correct in a given context, or why the SSH standard writers chose the terminology they did.

Your Answer

 

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.