RSA plaintext repetition attack, (same plaintext, different ciphertext)

Question

Billy wants to send a message to Bob. He generates secure primes p and q for each time he sends a message. However, he accidentally sends the same message multiple times. Is Billy's message still safe?

More formally, I know that e=3 and that the plaintext remains the same for more than 1 message, but the value of n (and subsequently the ciphertext, c) changes.

e=3
n=pq
c=123
plaintext=my-cool-mesage
e=3
n=p'q'
c=456
plaintext=my-cool-mesage

If an attacker has access to the e, n, and c for each message, can they recover the plaintext with the fact that the plaintext is shared, even when n changes?

OpenSSL RSA same plaintext but different cihertext - Not quite what I'm looking for, but close.
Find plaintext of RSA by solving extended euclidean algorith for two encrptions with two different exponents for same plaintext — Peter S, May 08 '21 at 06:54
The question in the second link above is no match either, because in the present question the moduli are different. The question certainly assumes textbook RSA (no random padding), and that the message is large enough and with enough entropy that each individual encryption would be safe. Here is a related question assuming three encryptions instead of two or "multiple". — fgrieu, May 08 '21 at 09:18
This link was what I was looking for: https://en.wikipedia.org/wiki/Coppersmith%27s_attack#H.C3.A5stad.27s_broadcast_attack — Peter S, May 08 '21 at 16:30

RSA plaintext repetition attack, (same plaintext, different ciphertext)

0 Answers0