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There's simply no way to know. I find it very unlikely that AES will be vulnerable to a ciphertext-only attack in the next 20 years (remember, it has been around for over 20 years already and attacks haven't gotten very far). There's no reason to believe the same won't be true for ChaCha20. If you use a good cipher with 256-bit keys (to avoid potential ...
5
You don't get empty output in AES, too. AES is a permutation and will always return a plaintext, correct or not depending on the key.
If I take the SHA3_512 of the Argon2ID-ed password and include it with the ciphertext, is the ciphertext now vulnerable to attacks?
One needs to find a pre-image to the key, and normally the cost of this is around $2^{512}$ ...
3
I know that theoretically, the security of the setup when used correctly is at least as secure as the most secure.
That's true if they use independent keys. If they use the same key, the security of the cascaded cipher may be much worse. Consider the case where cipher B happens to be the exact inverse of cipher A with the same key.
However, that doesn't ...
3
Playfair key grids are often generated by filling in the letters of a key phrase, then completing the grid with the remaining unused letters of the alphabet.
It looks to me like the partial grid you provided has been created in this way. If so, you can fill in several more letters straight away (assuming there is no J):
? A ? D ? ? A ? D ?
? ? ? ...
2
Real-world examples in which the OTP has been used:
In 1998, five Cuban intelligence officers of the Dirección de Inteligencia (DI), "The Wasp Network," were arrested by the FBI in the United States, and it was discovered that they had been receiving one-time-pad messages from a numbers station in Cuba called Atención, which transmitted at 17480 ...
2
Phil Zimmermann did not use DES or the RSA-owned RC-2 as models for the Bass-O-Matic cipher.
For the basis of that symmetric cipher, he used the work of a man named Charlie Merritt. Zimmermann's strong suit was not mathematics but programming in C, so he needed help. Merritt had called Zimmermann by phone (at Metamorphic Systems, a 1980 startup by Zimmermann)...
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