Assume an attacker obtained two ciphertexts and encrypted by the same key (a multi-time pad). We obtain that . Just by bitwise XORing these two ciphertexts we can obtain a wealth of information about the plaintexts, even though we can’t directly determine the keys or the plaintexts.
The following image from @houtvenCrypto1012017 demonstrates how multi-time pad ciphertexts of images can reveal information about the plaintexts.
