PSA_PAKE_STEP_ZK_PROOF macro

A Schnorr NIZKP proof. This is the proof in the Schnorr Non-Interactive Zero-Knowledge Proof (the value denoted by the letter 'r' in RFC 8235). Both for input and output, the value at this step is an integer less than the order of the group selected in the cipher suite. The format depends on the group as well: - For Montgomery curves, the encoding is little endian. - For everything else the encoding is big endian (see Section 2.3.8 of _SEC 1: Elliptic Curve Cryptography_ at https://www.secg.org/sec1-v2.pdf). In both cases leading zeroes are allowed as long as the length in bytes does not exceed the byte length of the group order. For information regarding how the group is determined, consult the documentation #PSA_PAKE_PRIMITIVE.