Source code for pksig_hess

""" 
Hess - Identity-based Signatures

| From: "Hess - Efficient identity based signature schemes based on pairings."
| Published in: Selected Areas in Cryptography
| Available from: Vol. 2595. LNCS, pages 310-324
| Notes: 

* type:           signature (ID-based)
* setting:        bilinear groups (asymmetric)

:Authors:    J. Ayo Akinyele
:Date:       11/2011
"""
from charm.toolbox.pairinggroup import PairingGroup,ZR,G1,G2,pair
from charm.toolbox.PKSig import PKSig
#import gc
#gc.disable()
#gc.set_debug(gc.DEBUG_LEAK)

debug = False

[docs]class Hess(PKSig): """ >>> from charm.toolbox.pairinggroup import PairingGroup >>> group = PairingGroup('SS512') >>> hess = Hess(group) >>> (master_public_key, master_secret_key) = hess.setup() >>> ID = "janedoe@email.com" >>> (public_key, secret_key) = hess.keygen(master_secret_key, ID) >>> msg = "this is a message!" >>> signature = hess.sign(master_public_key, secret_key, msg) >>> hess.verify(master_public_key, public_key, msg, signature) True """ def __init__(self, groupObj): global group,H1,H2 group = groupObj H1 = lambda x: group.hash(x, G1) H2 = lambda x,y: group.hash((x,y), ZR)
[docs] def setup(self): g2, alpha = group.random(G2), group.random(ZR) msk = alpha P = g2 ** alpha mpk = {'P':P, 'g2':g2} return (mpk, msk)
[docs] def keygen(self, msk, ID): alpha = msk sk = H1(ID) ** alpha pk = H1(ID) return (pk, sk)
[docs] def sign(self, pk, sk, M): if debug: print("sign...") h, s = group.random(G1), group.random(ZR) S1 = pair(h,pk['g2']) ** s a = H2(M, S1) S2 = (sk ** a) * (h ** s) return {'S1':S1, 'S2':S2}
# return (S1, S2)
[docs] def verify(self, mpk, pk, M, sig): if debug: print("verify...") (S1, S2) = sig['S1'], sig['S2'] a = H2(M, S1) if pair(S2, mpk['g2']) == (pair(pk, mpk['P']) ** a) * S1: return True return False
[docs]def main(): groupObj = PairingGroup('SS512') chch = Hess(groupObj) (mpk, msk) = chch.setup() _id = "janedoe@email.com" (pk, sk) = chch.keygen(msk, _id) if debug: print("Keygen...") print("pk =>", pk) print("sk =>", sk) M = "this is a message!" sig = chch.sign(mpk, sk, M) if debug: print("Signature...") print("sig =>", sig) assert chch.verify(mpk, pk, M, sig), "invalid signature!" if debug: print("Verification successful!")
if __name__ == "__main__": debug = True main()