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Signed-off-by: Alessandro Sorniotti <aso@zurich.ibm.com>

bccsp/schemes/aries/signer.go

@@ -56,6 +56,16 @@ func (s *Signer) getPoKOfSignature(
 
 	var pokOS *bbs12381g2pub.PoKOfSignature
 	if sigtype == types.Smartcard {
+		// this mode implements the protocol from https://eprint.iacr.org/2023/853.
+		// The protocol is between 3 parties, a user, a smartcard and a
+		// verifier, where user and smartcard can jointly convince a
+		// verifier they posses a tuple of attributes, one of which is
+		// only known by the smartcard.
+
+		// As such, we assume that `Nym` and `RNym` were generated by the smartcard
+		// and so we cannot prove their knowledge. We therefore pass them in to
+		// `NewPoKOfSignatureExt` as their as, since thier correctiness has already
+		// been proven by the smartcard in a separate proof.
 		messagesFr = append([]*bbs12381g2pub.SignatureMessage{{}}, messagesFr...)
 		C := Nym.Copy()
 		C.Sub(ipk.H0.Mul(RNym))