private_key = RSA.load_key('./my_rsa.priv')
private_key.sign(sha(data).digest())

their_public = RSA.load_pub_key('./their_rsa.pub')
their_public.verify(data, sig)

openssl dgst -sha1 -verify their_rsa.pub -signature /tmp/sig /tmp/data

mysig = priv.sign(sha(data).digest())
pub.verify(data, mysig)

private_key = RSA.load_key('./my_rsa.priv')
private_key.sign(data)?

def sign(self, digest, algo='sha1'):
        """
        Signs a digest with the private key
        @type digest: str
        @param digest: A digest created by using the digest method
        @type algo: str
        @param algo: The method that created the digest.
        Legal values are 'sha1','sha224', 'sha256', 'ripemd160', 
        and 'md5'.
        
        @return: a string which is the signature
        """
        digest_type = getattr(m2, 'NID_' + algo, None) 
        if digest_type is None:
            raise ValueError, ('unknown algorithm', algo)