Bitcoin Forum

def verify(r, s, z, public_key, k):
    w = modinv(s, n)
    u1 = z * w % n
    u2 = r * w % n
    R = E.lift_x(r)
    # Compute the candidate public key using the known k value
    candidate_public_key = u1 * G + u2 * R
    if public_key == candidate_public_key:
        print("Signature matches")
        return True
    else:
        print("Invalid signature")
        return False

def find_k_bruteforce(r, s, z, pub):
    i = 1
    max_iterations = 1000  # Add a maximum iteration limit
    while i <= max_iterations:
        k = (r * i + z) * modinv(s, n) % n
        print("i=", i, "k==", hex(k))
        # Verify the signature using the candidate k
        if verify(r, s, z, pub, k):
            print("Found k:", hex(k))
            return k
        else:
            print(f"Attempt {i}: Incorrect k value {hex(k)}")
        i += 1  # Increment i for the next iteration
    raise Exception("Failed to find a valid k value within the maximum iterations")

 

def verify(r, s, z, public_key, k):
    # Compute modular inverse of s
    w = modinv(s, n)
    
    # Compute u1 and u2
    u1 = z * w % n
    u2 = r * w % n
    
    # Compute R using the provided x-coordinate r
    R = E.lift_x(r)
    
    # Compute the candidate public key using the provided k value
    candidate_public_key = u1 * public_key + u2 * G
    
    # Check if the x-coordinate of the computed R matches that of the candidate public key
    if R[0] == candidate_public_key[0]:
        print("Signature matches")
        return True
    else:
        print("Invalid signature")
        return False