# Tag Info

## Hot answers tagged protocol-design

3

In your example, $Encryption_1$ is $\textsf{AES}_{CTR}$ and $Encryption_2$ is $\textsf{Salsa20}$. Then, the encryption method you are proposing is $Encryption_1(Encryption_2(plaintext))$, which is in fact a cascade of stream ciphers. Note that, because you simply XOR the streams, this cascade cipher commutes, that is, you will have the same result if you use ...

3

Asmuth and Blakley provided a proof that, assuming the keys for each cryptosystem are chosen independently, breaking their composite cryptosystem is at least as hard as breaking the hardest part of either. [1] Building on their work, cascade ciphers have been shown to in fact be harder to break than the hardest part of either. Admittedly, what you're ...

2

Dmitry's suggestion to use AES in counter mode sounds good to me, assuming that you only need confidentiality, and not integrity protection. (Counter mode, like most stream ciphers, is very malleable.) One trick you can use to save a bit of space is to use the current time as part of the nonce. (Of course, this only works if your devices have fairly well ...

2

A self-made modification to CBC is a bad idea, since your "IV" will not be random enough, whereas it must be truly random for CBC. Stream cipher is a good idea. You may use AES in the Counter mode, or you could use Salsa20, or any other eStream portfolio cipher (software and hardware implementations are available for all of them). Ensure that you have ...

1

You'll find the test vector in a draft "Test Vectors for the Stream Cipher ChaCha draft-strombergson-chacha-test-vectors-00" available at the following link: http://tools.ietf.org/html/draft-strombergson-chacha-test-vectors-00 The document links a github repo where you can find all the vectors https://github.com/secworks/chacha_testvectors/ Another ...

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