![]() For example when hashing, it's very important how the hashes are combined, and when you combine them in the wrong way, you might end up weakening your scheme significantly. ![]() Using plain, paddingless RSA, double encrypting with the same key wouldn't increase security at all, since composing RSA encryption results in a single RSA encryption with a combined key.īut that's not relevant in practice, since you don't typically encrypt data directly with RSA, and you almost always use padding.īut a lot depends on what you're doing. The main disadvantage of double encryption is that it's twice as slow. However, the key size used for encryption should. In the end, AES has never been cracked yet and is safe against any brute force attacks contrary to belief and arguments. Whatever breakthrough might crack 128-bit will probably also crack 256-bit. But in practice it'll likely increase security over the individual cipher. The difference between cracking the AES-128 algorithm and AES-256 algorithm is considered minimal. In practice likely stronger than the stronger, but that's not guaranteed. Using different keys makes the encryption at least as strong as the stronger of the encryptions you use. Where h a s h is an arbitrary hash function and e n c an. Compute the ciphertext c e n c k ( h) e n c k ( h a s h ( d a t a)). There are two different cases: Encryption using the same key, and encryption using two independent keys. Now Im wondering what the security of the following 'idea' would be (Im sure that there a good reasons why it is not used as it is more simple than HMAC or CBC-MAC): Compute the hash value h h a s h ( d a t a).
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