Linked Questions

35 votes
5 answers
6k views

What security do Cryptographic Sponges offer against generic quantum attacks?

In the face of non-quantum attacker, Keccak[r=1088,c=512] with 512 bits of output provides: Collision resistance up to $2^{256}$ operations Preimage resistance up to $2^{256}$ operations Second ...
Nakedible's user avatar
  • 1,440
31 votes
3 answers
85k views

Why we can't implement AES 512 key size?

Out of curiosity why we can't implement AES 512 key size? Please explain somehow i can understand! I'm not an expert.
hamedb71's user avatar
  • 511
16 votes
3 answers
22k views

Has AES-128 been fully broken?

Has AES-128 been broken over the full 10 rounds? If so, by what means? By a commercial entity? By a supercomputer? If not, why is AES-256 used to replace AES-128 so frequently?
Offir's user avatar
  • 283
14 votes
5 answers
9k views

Does Grover's algorithm really threaten symmetric security proofs?

By Shannon's theorem of perfect security, if I give you a ciphertext 'LOUPL', you can do a brute-force attack and then you would find plaintexts like 'HELLO', 'APPLE', 'SPOON', but you can't ...
Victor Espinoza's user avatar
7 votes
3 answers
8k views

Can Quantum Computers crack RSA and AES?

Im trying to learn more about cryptography and ran into a post, Is AES-128 quantum safe?, which asks if AES-128 is safe. From the articles and replies it seems that AES-128 (symmetric key) is safe ...
cryptoman534345's user avatar
9 votes
2 answers
3k views

What is a multi-target attack?

What exactly is a multi-target attack? How does the attack work on different cryptographic schemes (block ciphers, hash functions, elliptic curves)? How can it be avoided?
Conrado's user avatar
  • 6,414
6 votes
2 answers
484 views

"Cropping" the resulting shared secret from ECDH

I'm deriving a shared secret using ECDH with Ed25519 keys. According to the specification (page 5), the shared secret then can be any valid Curve25519 public key, i.e. any valid 32 bytes. My ...
user avatar
3 votes
4 answers
488 views

Increasing Block Length of Symmetric Cipher

Triple DES (using an existing cipher 'DES' of key length 56bits) provides security of 112bits (although it requires key material of 168bits). Does there exist a mechanism to increase block length of ...
crypt's user avatar
  • 2,397
1 vote
3 answers
3k views

What's the preferable encryption for large data and files in terms of speed and security other than AES?

First of all, I'm relatively new to encryption so please bear with me. I'm looking for a way to encrypt large amounts of data only on my device, no need to transfer my encrypted files/data (10-20GB or ...
Ilkay Solotov's user avatar
1 vote
1 answer
324 views

Quantum computer threats to modern cryptography

I am having a university assignment that requires me to study on the threats that quantum computer poses to modern cryptography. At the moment, I know that modern symmetric encryption will reduce ...
Hern's user avatar
  • 159
0 votes
1 answer
146 views

Do multiple keys mitigate Grover algorithm?

Grover, a quantum algorithm, weakens AES and ChaCha20. Is it possible to use multiple symmetric keys to encrypt a message multiple times to achieve 256-bit security for quantum computers?
Flan1335's user avatar
  • 361
1 vote
1 answer
100 views

Encrypting with CBC then XORing repeatedly a chunk of random data smaller than the plaintext: Is there a gain in security?

If I encrypt a 1MiB file with AES-CBC (or any other cipher) and XOR a 128KiB of (truly) unpredictable random data repeating until the end of file, will I have a security of 1048576-bits (128KiB*8)? ...
phantomcraft's user avatar