Welcome

This webapp offers a number of challenges in attacking the RSA and El Gamal cryptosystems. Each attack is meant to illustrate a way to misuse RSA or El Gamal; when they are used correctly, they are not vulnerable to any of these attacks.

Challenge Name		Challenge Description
RSA Challenge One	Small Message Space Attack	Given an RSA ciphertext encrypting one of several messages, recover the message.
RSA Challenge Two	Small Plaintext and Encryption Exponent Attack	Given an RSA ciphertext encrypting a small message with a small public key (e.g. e = 5), recover the message.
RSA Challenge Three	Broadcast Attack	Given RSA ciphertexts with different moduli but the same low encryption exponent, recover the message.
RSA Challenge Four	Modulus Reuse Attack	Given an encryption key, a decryption key and a modulus, recover the decryption key corresponding to a different encryption key but the same modulus.
El Gamal Challenge	Randomness Reuse Attack	Given an encryption key, two ciphertexts which use the same random exponent y and the plaintext corresponding to one of those ciphertexts, recover the second plaintext.

This material is based upon work supported under Air Force Contract No. FA8721-05-C-0002 and/or FA8702-15-D-0001. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. Air Force.