Source code for pksig_bls04

'''
**Boneh-Lynn-Shacham Signature (BLS04)**

*Authors:* D. Boneh, B. Lynn, H. Shacham

| **Title:** "Short Signatures from the Weil Pairing"
| **Published in:** Journal of Cryptology, 2004
| **Available from:** https://crypto.stanford.edu/~dabo/pubs/papers/BLSmultisig.html
| **Notes:** This is the IBE (2-level HIBE) implementation of the HIBE scheme BB_2.

.. rubric:: Scheme Properties

* **Type:** signature (identity-based)
* **Setting:** bilinear groups (asymmetric)
* **Assumption:** CDH

.. rubric:: Implementation

:Authors: J. Ayo Akinyele
:Date: 1/2011
'''
from charm.toolbox.pairinggroup import PairingGroup, ZR, G1, G2, pair
from charm.core.engine.util import objectToBytes
from charm.toolbox.IBSig import *


debug = False




class BLS01(IBSig):
    """
    >>> from charm.toolbox.pairinggroup import PairingGroup
    >>> group = PairingGroup('MNT224')
    >>> messages = { 'a':"hello world!!!" , 'b':"test message" }
    >>> ib = BLS01(group)
    >>> (public_key, secret_key) = ib.keygen()
    >>> signature = ib.sign(secret_key['x'], messages)
    >>> ib.verify(public_key, signature, messages) 
    True
    """
    def __init__(self, groupObj):
        IBSig.__init__(self)
        global group
        group = groupObj
        


    def dump(self, obj):
        return objectToBytes(obj, group)

            


    def keygen(self, secparam=None):
        g, x = group.random(G2), group.random()
        g_x = g ** x
        pk = { 'g^x':g_x, 'g':g, 'identity':str(g_x), 'secparam':secparam }
        sk = { 'x':x }
        return (pk, sk)

        


    def sign(self, x, message):
        M = self.dump(message)
        if debug: print("Message => '%s'" % M)
        return group.hash(M, G1) ** x

        


    def verify(self, pk, sig, message):
        M = self.dump(message)
        h = group.hash(M, G1)
        if pair(sig, pk['g']) == pair(h, pk['g^x']):
            return True  
        return False 






def main():
    groupObj = PairingGroup('MNT224')
    
    m = { 'a':"hello world!!!" , 'b':"test message" }
    bls = BLS01(groupObj)
    
    (pk, sk) = bls.keygen()
    
    sig = bls.sign(sk['x'], m)
    
    if debug: print("Message: '%s'" % m)
    if debug: print("Signature: '%s'" % sig)     
    assert bls.verify(pk, sig, m), "Failure!!!"
    if debug: print('SUCCESS!!!')



if __name__ == "__main__":
    debug = True
    main()