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2 votes

Do I need to use unique IVs if all encrypted data is unique?

Is this necessary for my use case? I've read that this is done so encrypting the same data twice does not result in the same ciphertext, but in my case this is exactly the necessary behavior. Making ...
poncho's user avatar
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1 vote

Encrypting the nonce in AES-CCM

ECB mode is a bit of a misnomer if just a single input value is used. At that point it is just a single block cipher encrypt. CCM only assumes that a unique nonce is used, it doesn't require an ...
Maarten Bodewes's user avatar
  • 92.4k
1 vote
Accepted

What exactly is RSA_WITH_AES256_CBC_SHA256?

This is about a hybrid cryptosystem where a key encapsulation mechanism is combined with a symmetric cipher. The field is expanding, for instance because of the advent of PQC algorithms. Several ways ...
Maarten Bodewes's user avatar
  • 92.4k
4 votes

What best to put in unused nonce bytes when using AES-GCM-SIV

In short yes, nonces just need to be unique. Just zeroing "leftover" bytes is fine if your protocol can guarantee uniqueness with fewer bytes. In protocols the zero bytes are often ...
Maarten Bodewes's user avatar
  • 92.4k
0 votes

Find two hard to reverse functions f and h such that f ∘ h ∘ g = h (f and h injective, no constraints on g)

It is essentially key exchange: let $x$ be the input, $g$ encrypts $x$ using public key 1, $h$ encrypts the result using public key 2, and then $f$ decrypts the result using private key 1, where ...
xacid's user avatar
  • 74
0 votes

Given and encrypted message, is it theoretically possible to decrypt a message without the key or guessing it? If so, what methods could be used?

In general no, properly applied AES+CBC with proper key and IV is secure. Known attacks are far from practical. However, if the message is guessable, there are many practical scenarios where one could ...
Meir Maor's user avatar
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