Topic: def for divide and plus minus nonce in transaction (Read 185 times)

p = 0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f

n = 0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141

E = EllipticCurve(GF(p), [0, 7])

G = E.point( (0x79be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798,0x483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8))   # Base point

def egcd(a, b):

    if a == 0:

        return (b, 0, 1)

    else:

        g, y, x = egcd(b % a, a)

        return (g, x - (b // a) * y, y)

def modinv(a, m):

    g, x, y = egcd(a, m)

    if g != 1:

        raise Exception('modular inverse does not exist')

    else:

        return x % m
    
def verify(r, s,z,public_key):
    w = int(modinv(s, n))
    u1 = int((z * w) % n)
    u2 = int((r * w) % n)
    D=u1*G + u2*public_key
    x,y=D.xy()
    x=int(x)

    if (r % n) == (x % n):
        print( "signature matches")
        return 1
    else:
        print("invalid signature",r,x%n,hex(int(x%n)))
        return -1  

def sign(privkey,nonce,message):
    z=message
    nonceG=nonce*G
    rx,rye=nonceG.xy()
    rx=int(rx)
    s=(z+int(rx)*privkey)*modinv(nonce,n)%n
    return int(rx), int(s), int(z)


def make_minus(k_minus,r,s,z,pub):
    w = int(modinv(s, n)%n)
    u1 = int((z * w) % n)
    u2 = int((r * w) % n)
     
    D=u1*G + u2*pub
     
    du= D-k_minus*G
    x,y=du.xy()
    r_new=Integer(x)
    #c = E.lift_x(Integer(r)) - k_minus * G
    #print("c",du)
   
    s_new = s * modinv(r,n) * r_new % n
    h_new = (z - s * k_minus) * modinv(r,n) * r_new % n
    return int(r_new),int(s_new),int(h_new)

def make_divide(r,s,z,how_much,pub):
    w = int(modinv(s, n)%n)
    u1 = int((z * w) % n)
    u2 = int((r * w) % n)
     
    D=u1*G + u2*pub
    R=D*modinv(how_much,n)
    r_new=int(R.xy()[0])
    #with the same pubkey
    dsa=int(s*modinv(r,n)%n)   # dsa = s * 1/r
    
    dma= int(z*modinv(r,n)%n)  # dma = z * 1/m
     
    dsa = dsa*how_much *r_new%n 
    m=dma*r_new%n
     
    s_new=dsa
    z_new=m
    return r_new,int(s_new),int(z_new)



# input values:

private=100
pub=private*G
nonce=200
message=11111111111111111111111111111111


# first transaction

r,s,z = sign(private,nonce,message)


#test 1
#test for plus and minus nonce in transaction

k_minus = 100 

#output must be nonce=100 with the same pubkey
r1,s1,z1=make_minus(k_minus,r,s,z,pub)
#verify new transaction
verify(r1,s1,z1,pub)

k=(r1*private+z1)*modinv(s1,n)%n
print("new nonce==",k)

# test 2
#test for divide nonce in transaction
#output must be nonce=100 with the same pubkey

how_much=2 #we divide by 2 nonce in transaction 
r2,s2,z2=make_divide(r,s,z,how_much,pub)
#verify new transaction
verify(r2,s2,z2,pub)

k=(r2*private+z2)*modinv(s2,n)%n
print("new nonce==",k)