Cryptography trying to implement signature of ElGamal

---

trying to implement signature of ElGamal Posted: 22 Dec 2018 08:49 AM PST I'm trying to implement the signature algorithm of ElGamal. The steps I'm following are: Choose a random number h ∈ [2,p – 2] that is coprime with p - 1, i.e., gcd(h, p-1)=1. Calculate r = alpha^h mod p Calculate s = (m – d · r) · h^–1 mod p – 1 ​ Note: k_priv is the tuple with (prime, alpha, d) ​ My code is: from math import gcd from operator import mod def elgamal_sign(k_priv, m, k=None): if k is not None: h = k else: h = random.randrange(2, k_priv[0]-2) while True: if gcd(h, k_priv[0]-1) == 1: continue r = pow(k_priv[1], h, k_priv[0]) d = k_priv[2] h_inverse = pow(h, -1) dummy = (m - d * r) * h_inverse s = mod(dummy, k_priv[0]-1) return r, s Suppose the following values: m = 42 k_priv = (141627058957340093855620484680587497231, 49407674567884478422262585667470127500, 91557801542207645804476483173676169513) h = 6505205550934361491179720631243 exp_r = 16070586247864526048715174304611921161 exp_s = 79906657969558945308772045181673566953 For r, I'm getting the proper value but not for s (I get 2.9919091950952993e+37 instead of exp_s), so I guess my formula of calculating s is wrong. submitted by /u/daviddoji [link] [comments]

First time noob using SFTP. Help needed. Posted: 22 Dec 2018 12:06 PM PST Hello, I'm trying to use FileZilla to connect to a server via sftp. I was given a username, password, and a PGP Signature with a .asc extension. All works well until I get an "Authentication failed." error. I assume I need to add a key file in the Public Key Authentication settings page in FileZilla, but all I have is that PGP signature. How would I go about using this .asc file to get the necessary key? ​ submitted by /u/Pyqtenoch [link] [comments]

You are subscribed to email updates from Cryptography news and discussions. To stop receiving these emails, you may unsubscribe now.	Email delivery powered by Google
Google, 1600 Amphitheatre Parkway, Mountain View, CA 94043, United States