[Interest] Integrate crypto in Qt project
konrad at silmor.de
Mon Jan 8 13:13:23 CET 2018
On Mon, January 8, 2018 12:05, Christophe Thomas wrote:
> Thx for your feedback,
> Don't worry I won't even imagine using some unknown third party code for
> crypto in production code.
> Since yesterday I've continued studying my case and my problem is that I'm
> bounded to a specific format: I'm trying to implement some map (S63
If it is only decryption (or verification) you may be fine. For encryption
you have to know rather more than what is usually documented (there are
some hidden traps in implementing this).
> This format is using
> - blowfish as encryption/decryption method => so no real choice here for
> me, but you are right I will use openssl instead of some other code for
Since this forces you to implement the protocol level yourself, I'd
recommend libgcrypt - it is much easier to use than the OpenSSL low level
> - DSA keys and signature are provided in plain text format (see below), so
> my main concerne is to build the key or signature with those data in order
> to launch DSA verify command. I'm now thinking of manually building the
> data in DER/ASN.1 format but if I can do things directly it would be
Don't do DER (or BER, CER, ...) yourself if you can avoid it. It is an
endless source of sorrow...
With libgcrypt you build an S-expression structure directly from the text
values using gcry_sexp_build and use this structure to feed the public key
functions. No need to mock about with ASN.1.
If this is a commercial project and your company can afford it: I'd
recommend to hire a cryptography expert for a few days to either implement
the crypto stuff directly or at least to review the code.
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