# Tag Info

5

For many areas of encryption, you actually DO want as truly random of a value as possible. Primes (or more accurately, relative primes) only enter in to the equation when dealing with certain forms of asymmetric encryption. Asymmetric encryption is where one person has a public key to encrypt a message and then the recipient has a different private key ...

5

XSalsa20 uses the same cryptographic core as Salsa20 and comes with a security proof that it's secure if Salsa20 is secure. It doesn't use the core of ChaCha and thus has worse diffusion. The way XSalsa20 works is that it hashes its 256 bit key and the first 128 bits of the nonce using HSalsa down to a 256 bit key and then uses that key together with the ...

3

No, because then you could calculate $z_1 \oplus z_2 = (m_1 \land m_2) \oplus (m_1 \lor m_2) = m_1 \oplus m_2$. In practice, you can only find $m_1 \oplus m_2$ if both $m_1$ and $m_2$ are encrypted with the same OTP (i.e., $(m_1 \oplus y_1) \oplus (m_2 \oplus y_1) = m_1 \oplus m_2$). So without any knowledge of $m_1$, $m_2$, $y_1$ or $y_2$, there is no way ...

3

The comments on the question are very good. That said, I'll try to address the question(s). What factors should I consider so that it does not become weaker? This is a very important concern that I am glad you have. One of the big strengths that standard ciphers have is that lots of really smart people have looked at them and have not been able to ...

1

What you are describing is One-Time-Pad encryption, and yes it does have perfect secrecy. Note that for any ciphertext $y$ there is exactly one key $k'$ for each possible plaintext $x'$ so that $E_k(x') = y$. So if you choose the key uniformly at random the ciphertext gives no information on the plaintext, because any plaintext is equally likely.

1

I suggest Vigenère cipher, it is fun on paper and also you can be creative in using key. you can use your phone number as key or your entire family phone number in age order. Key: ABCDABCDABCDABCDABCDABCDABCD Plaintext: CRYPTOISSHORTFORCRYPTOGRAPHY Ciphertext: CSASTPKVSIQUTGQUCSASTPIUAQJB http://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher

1

For confidentiality purposes? one time pad (when possible) rc4 (because you can by hand)

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