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[Help-gnutls] Re: verify signed data
From: |
Simon Josefsson |
Subject: |
[Help-gnutls] Re: verify signed data |
Date: |
Mon, 19 Mar 2007 10:03:43 +0100 |
User-agent: |
Gnus/5.110006 (No Gnus v0.6) Emacs/22.0.95 (gnu/linux) |
Volker Steiß <address@hidden> writes:
> Hello everybody,
>
> I am on a project using public-private-key methods and just tried using
> GnuTLS for this.
> I am stuck at this point and hope someone can help me out:
> First I created a public private key (it's long ago, so I cant tell you how I
> did it exactly).
> I have created a signature with gnutls_x509_privkey_sign_data(PRIV_KEY),
> converted it to readable text with gnutls_hex_encode() and stored the result
> (Data + Signature) into a file.
> Now I want to verify the created data: I read the data and the signature,
> decode the signature with gnutls_hex_decode() and try to verify it with
> gnutls_x509_privkey_verify_data(PUB_KEY). But here I get return code 0, which
> means no success.
>
> Verification overview:
>>>>> - somecode
> init_gnutls ()
> ...
> gnutls_hex_decode (&temp, signature.data, &signature.size)
> ...
> gnutls_x509_privkey_init (&key)
> gnutls_x509_privkey_import (key, &key_datum, GNUTLS_X509_FMT_PEM)
> result = gnutls_x509_privkey_verify_data (key, flags, &uid, &signature)
> //result = 0
> ...
> <<<< - end of somecode
>
>
> Btw: What I realize at "gnutls_hex_decode (&temp, signature.data,
> &signature.size)" is that temp.size is 512 bytes and signature.size also is
> 512. Am I wrong when I say: It should be smaller after decoding?
Did you check errors from all functions? Hex decoding a 512 byte
string should not give another 512 byte string. Did you allocate a
signature.data buffer before calling gnutls_hex_decode?
Btw, if you aren't sure that you must use these functions, you
probably want to use a higher-layer message signature format instead
of low-level sign/verify primitives. Standard formats for this is
OpenPGP (try GnuPG) and CMS/SMIME (try gpgsm).
/Simon