I typically divide the problem in two.
Do a raw public key operation. If you see something that looks random,
then the public key doesn't match the private key used to generate the
signature, or either the public key or signature has been altered. If
it looks like padding + OID + hash, then
Here is the vector and code that is provided in the link:
/*
VECTOR SOURCE: csrc.nist.gov/groups/STM/cavp/documents/dss/RSAVS.pdf
B.1.3 SigVerRSA.req., it's "Result = P" as per B.3.3 SigVerRSA.rsp
# CAVS 3.2
# "SigVer RSA (X9.31)" information for "testshas"
# Mod sizes selected: 1024 1536
# SHA A
[mailto:owner-openssl-us...@openssl.org] On Behalf Of Dave Thompson
Sent: Saturday, January 31, 2009 8:11 AM
To: openssl-users@openssl.org
Subject: RE: Openssl signature verification
> From: owner-openssl-us...@openssl.org On Behalf Of Ajeet kumar.S
> Sent: Friday, 30 January, 2009 00:07
> From: owner-openssl-us...@openssl.org On Behalf Of Ajeet kumar.S
> Sent: Friday, 30 January, 2009 00:07
> In openssl API X509_verify(X509 *a, EVP_PKEY *r) is used to verify
> the signature of certificate. I have some doubt please help me.
> Is in this API we are passing the CA certificate and
