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Apr
9
comment Question about "toy: streamcipher
Is that scan from a textbook? Because if so, the mangled English and general lack of copyediting suggest that it's probably not very high quality. (If it's from an instructor's personal handouts, that could perhaps be excusable, at least if English isn't their native language. Although, even so, the broken grammar surely can't be making the material any easier to understand for the students.)
Apr
5
awarded  encryption
Apr
4
awarded  Nice Answer
Apr
4
answered Does composing multiple substitution ciphers improve security?
Apr
4
comment Decoding the Playfair cipher with a crib
This is, IMO, a perfect example of a useful duplicate question; the linked question does provide the answer, but there's no way you'd guess that from the title. Upvoted and voted to close. :)
Apr
2
awarded  Nice Answer
Mar
25
awarded  Nice Answer
Mar
14
revised Why do we need Euler's totient function $\varphi(N)$ in RSA?
added 1567 characters in body
Mar
14
comment Reverse Encryption Algorithm from Decryption code
The trick with SO is that "asking for code" is really more about how you ask your question than about what you ask. You want to stand out from the "gimme teh codez 4 my homework now" crowd, so you need to phrase your question as "please teach me how to do this myself" instead of "please give me code I can copy-paste". That's really all there is to it.
Mar
14
revised Reverse Encryption Algorithm from Decryption code
added 273 characters in body
Mar
14
comment Reverse Encryption Algorithm from Decryption code
This is a decent question, and I've answered it below (although only partially so far, just in case it's an exercise you're supposed to complete on your own). However, I'm not 100% sure it really belongs on this site; it might be better suited for Stack Overflow, or perhaps for Reverse Engineering. If others feel the same way, we could always ask for a mod to migrate it.
Mar
14
revised Reverse Encryption Algorithm from Decryption code
edited tags
Mar
14
revised Reverse Encryption Algorithm from Decryption code
added 1230 characters in body
Mar
14
answered Reverse Encryption Algorithm from Decryption code
Mar
14
answered Why do we need Euler's totient function $\varphi(N)$ in RSA?
Mar
13
revised How do I attack an RSA setup where e is even?
edited tags
Mar
13
comment How do I attack an RSA setup where e is even?
This isn't really RSA, but a variant of the Rabin cryptosystem. See e.g. this question for the difference.
Mar
3
comment Attack being kind of completely puzzled?
Honestly, I don't understand it either. Maybe it needs more context (I haven't actually read the paper), or maybe something got lost in translation?
Mar
3
comment Entropy calculation
@Mok-KongShen: If you only measure the entropy of the single-character frequencies, yes (because, by definition, that distribution ignores the order of the characters). If you instead measured, say, the distribution of consecutive groups of $n$ characters (where $n > 1$), the randomly shuffled sequence would have a much higher entropy than the sorted one.
Mar
3
awarded  hmac