github.com/true-sqn/fabric@v2.1.1+incompatible/idemix/weak-bb.go (about)

     1  /*
     2  Copyright IBM Corp. All Rights Reserved.
     3  
     4  SPDX-License-Identifier: Apache-2.0
     5  */
     6  
     7  package idemix
     8  
     9  import (
    10  	"github.com/hyperledger/fabric-amcl/amcl"
    11  	"github.com/hyperledger/fabric-amcl/amcl/FP256BN"
    12  	"github.com/pkg/errors"
    13  )
    14  
    15  // WBBKeyGen creates a fresh weak-Boneh-Boyen signature key pair (http://ia.cr/2004/171)
    16  func WBBKeyGen(rng *amcl.RAND) (*FP256BN.BIG, *FP256BN.ECP2) {
    17  	// sample sk uniform from Zq
    18  	sk := RandModOrder(rng)
    19  	// set pk = g2^sk
    20  	pk := GenG2.Mul(sk)
    21  	return sk, pk
    22  }
    23  
    24  // WBBSign places a weak Boneh-Boyen signature on message m using secret key sk
    25  func WBBSign(sk *FP256BN.BIG, m *FP256BN.BIG) *FP256BN.ECP {
    26  	// compute exp = 1/(m + sk) mod q
    27  	exp := Modadd(sk, m, GroupOrder)
    28  	exp.Invmodp(GroupOrder)
    29  
    30  	// return signature sig = g1^(1/(m + sk))
    31  	return GenG1.Mul(exp)
    32  }
    33  
    34  // WBBVerify verifies a weak Boneh-Boyen signature sig on message m with public key pk
    35  func WBBVerify(pk *FP256BN.ECP2, sig *FP256BN.ECP, m *FP256BN.BIG) error {
    36  	if pk == nil || sig == nil || m == nil {
    37  		return errors.Errorf("Weak-BB signature invalid: received nil input")
    38  	}
    39  	// Set P = pk * g2^m
    40  	P := FP256BN.NewECP2()
    41  	P.Copy(pk)
    42  	P.Add(GenG2.Mul(m))
    43  	P.Affine()
    44  	// check that e(sig, pk * g2^m) = e(g1, g2)
    45  	if !FP256BN.Fexp(FP256BN.Ate(P, sig)).Equals(GenGT) {
    46  		return errors.Errorf("Weak-BB signature is invalid")
    47  	}
    48  	return nil
    49  }