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comment Theoretical Mathematics & Cryptography
Advanced mathematics are the tools for understanding, designing and finally breaking cryptosystems. If you don't have the basics and the tools, you can't achieve anything - in any science.
Jun
26
comment How to write automaticaly server generated keys into a file?
On one hand it is quite unclear what your question is, and on the other hand it is probably not about cryptography, but some implementation issues. Those are off-topic on this page, and either SO or security-SE might be a better fit.
Jun
25
comment Why is the public/private key length used in libsodium so much shorter than needed for RSA
This question appears quite off-topic, since only guesswork can be done to answer this. Anyway, public key crypto with 256 bit can be done - just not with RSA and dlog-based crypto in $\mathbb{F}_p$.
Jun
23
comment Is secure communication without public-key crytography feasible?
What are your actual assumptions about the initial setup? What do parties know of each other? Is there some trusted third party, a public bullet board, a PKI with certificates? Basically: If you got no prior knowledge of each other and trust no one else, you can't build any form of authentication.
Jun
22
comment Is Encryption without knowing the input directly possible at all?
If all the $t_i$ are known to everyone, this works, because everyone can check the output of Bob, when he revealed his key. Basically this is like a commitment scheme. However, this way Alice will also find out later who got which text, after Bob revealed his key. All you need then is a proof that Alice actually used those commitments and used each one just once.
Jun
22
comment Is Encryption without knowing the input directly possible at all?
The enitre point of ZKP is that it is a proof to other people. This answer does not address the question at all.
Jun
22
comment What is more efficient, pairing based cryptography or non pairing based cryptography?
It's pretty obvious: Pairings are useful, if you need pairings. If you don't then, they aren't. Moreover, in pairing friendly groups the "normal" DH problem is easy to solve, so just transferring schemes from one group into the other might pose problems.
Jun
19
comment Why are there only positive value points on an elliptic curve?
It seems, the entire argument and answer is about "In $\mathbb{F}_p$ you actually have to calculate numbers modulo $p$". Be that the shorthand of the format $-x$ instead of $p-x$ or inversion for numbers like $1/2$.
Jun
18
comment Exist this chat protocol?
Eve can just say "Look, I am the server. Use this random key for your next exchange". The protocol is almost trivial, and has barely any protection at all. Basically this is a "hello world" example at best.
Jun
12
comment RSA private key d knowing e,n
How about trying out the $d$ value and see if you get the correct output? With those characteristics of $p$ and $q$, Fermat's factoring method would probably be quite fast (both prime factors close together).
Jun
10
comment Vigenère cipher frequency analysis not working
Since no one is talking like Shakespeare today, there are differences in language characteristics. For example, in his works the word thou (and its different cases, e.g. thee, thy) is used quite a lot, but in any modern english this would be you instead => leads to an increase in t and a decrease in y
Jun
9
comment Vigenère cipher frequency analysis not working
After a quick glance with an online tool: You're right, and the frequency discrepancy comes from the plain text. Literature can be tricky for frequency analysis, since they utilize the language in uncommon ways.
Jun
9
comment Vigenère cipher frequency analysis not working
ah, you are not sure about the keylength yet. That explains quite a bit. Good luck on trying.
Jun
9
comment Vigenère cipher frequency analysis not working
Maybe just run the frequency analysis on the actual text? It is possible, that this part of text does not fit the standard language distribution (don't forget, it takes every 12th symbol). And did you encounter similar problems with the other ensembles of characters (chars at 2,14,26,... ; 3,15,27,...;...)?
Jun
8
comment Pailler encryption of small integers to 32-bit integers
Except the implementation part, this answer is correct. If you adapt $n$, s.t. ciphertexts fit into the range of 32 bits, the factorization of $n$ is trivial. If you say $n^2 \approx 2^{32}$ (ciphertext space is mod $n^2$), prime factors of $n$ are around 8 bits. Even if you say you pick a larger $n$, and just have to find $r$,s.t. the ciphertext falls into this range, you can't make that work.
Jun
8
comment Is it OK to encode data using key equal to data
Also see Is there a format preserving cryptographically secure hash? for a construction of such a oneway function.
Jun
8
comment Is it OK to encode data using key equal to data
The question is lacking the actual goal. Do you want a one-way function similar to a hash? Then this construction works, but doesn't offer an advantage over standard hash functions. Or do you want to be able to decipher them again? Then this construction is bad (because you basically have to store the string as key).
Jun
8
comment Will adding space to the Vigenère block make it truly unbreakable?
If you use a random permutation over 27 symbols (letters + space) and you use a key of the length of the ciphertext, then you get a bloated version of OTP. All it does, is increase the already huge size of the key (since the whole permutation for each symbol requires $27$ symbols to be stored, instead of just one).
Jun
3
comment Can you identify this algorithm?
You really shouldn't be using this. In a commercial application, this is a huge financial risk. The effort to break this is practically close to zero. Basically, this could be a backdoor to the entire system. And on a scale I would rate it much, much worse than bad (none) password policies.
Jun
1
comment Lightweight hash function
Yes you are. To be honest, the question is quite on the edge to be off-topic (reference recommendation), as it is missing any information about research done, an actual non-general question, etc.