Mok-Kong Shen
• Member for 9 years, 4 months
• Last seen more than 4 years ago

There was a telegraphic code that mapped the comparatively frequently used 10000 words (that's very much more than for common daily use, e.g. newspapers) of Chinese to [0,9999]. There was once also a ...

In his answer Michael mentioned a known stego scheme of using the first characters of words/sentences as stego characters and rightly remarked that the scheme can be practically applied ("user-...

That's a well-known disadvantage of using OTP. Like in the ancient times, you could e.g. employ a trusted courier for that transfer.

The algorithm of Fisher and Yates (see Knuth, The Art of Computer Programming, vol. 2) does a pseudo-random permutation of a sequence without however avoiding possible duplicates in your sense. One ...

LFSR as such isn't a CSPRNG. There are diverse CSPRNGs, see crypto textbooks, also A. Menezes et al., Handbook of Applied Cryptography (freely available online). I have a code for a CSPRNG based on ...

Instead of using probabilistic methods to generate large primes, as indicated in the other answers, one can (IMHO better) employ Maurer's algorithm of generating provable primes. I have a Python code ...

It's a matter of periods in the sequence of numbers generated by the PRNG. If the output of the PRNG has a single period that is of length $2^n$, then you can avoid repetition by appropriately ...

You would need (at least) 3 pairs of vectors in order to determine the 3*3 matrix.

As its name indicates, a block cipher is an algorithm to encrypt (with a secret key) plaintexts in chunks of a certain fixed block size. For practical reasons, software of a block cipher has only one ...

Yes. See also en.wikipedia.org/wiki/Advanced_Encryption_Standard. There is a pseudo-code in NIST's AES standard document which is very helpful for implementors. I have a Python code that very closely ...

The theoretically correct random permutation algorithem is IMHO uniquely that of Fisher and Yates [1], which needs for performing a permutation of a sequence of n items n-1 PRNs. I perviously found ...

I have a very simple code of doing steganography that neither modifies any word of your original text nor poses any constraints on the words you employ in the text; it simply changes a little bit of ...

Text steganography is by nature more difficult to do than image steganography, if high security is demanded. For good results one has to accept the trade-off of lower stego bit-rates, which could be ...

[Copy of my answer in another community:] In the RC6 specification (see de.wikipedia.org/wiki/RC6) S[*] designates an array of 2r+4 round keys, whose size in bits you can choose in the range [0,2000]. ...

Since a good block encryption algorithm, e.g. AES, running in counter mode, i.e. encrypting some more or less arbitrary chosen (unknown to the opponent) input values, is generally considered to be ...

When a contract in digital from is to be signed online by Alice and Bob, an issue concerning the fairness of the signing process crops up as follows: If Alice first signs the document and sends it to ...

I devised a (presumably non-conventional) scheme which re-formats an input text stream like emails a little bit such that the number of words in a line of the output file mod 2 gives the stego bit in ...

I suppose you could use the initial passphrase as the key of a block cipher to encrypt a session dependent non-secret data, e.g. date and message serial number etc., and use that for your purpose.

I have implemented Maurer's algorithm of generating random provable primes (see Menezes et al., Handbook of Applied Cryptography) in Python, which is, as comparison showed, only moderately slower than ...

Maurer has an algorithm to generate random, almost uniformly distributed, k-bit primes that are provably prime, in contrast to schemes that generate highly probably primes (commonly employing the ...