# All Questions

688 views

### How to encrypt a short string and keep the length secret

I need to encrypt relatively short strings (generally less than 100 characters). If possible, I want to avoid leaking the length of these strings. How can I do that? The thing that came to my mind is ...
502 views

### Calculating cycles per byte

Cycles per byte seems to be a critical concern in designing and choosing stream ciphers. For example, from Wikipedia, RC4 has 7 cycles/byte on original Pentium chips. How is this calculated? Do they ...
203 views

### Randomized stream cipher using multivariant quadratic equations

This is an idea I had for cipher that I thought might reduce to a known hard problem. It is efficient (compared to something like BBS) in terms of time but not in terms of space. Here's the ...
253 views

### Idea for user/pass hashing to prevent rainbow tables, would it work?

I'm very new to cryptography (and security in general, for that matter), but I had an idea that I'm sure is very flawed, but is worth asking. If a computer user, online account, etc, needs to verify a ...
1k views

### Is RSA in a ECB-like-mode safe for bulk encryption?

Let's say I would like to communicate with my friend using asymmetric/public-key encryption, e.g. RSA. (Note: I do realize that in practice this is done through an intermediate symmetric key, but ...
430 views

### Trying to find a different DES encryption system explanation

I need a mathematical explanation of what does the DES encryption system really do. This means I need more explanation than the one that offers FIPS, which is more an explanation for computer ...
92 views

### Discrete logarithm modulo a smooth number

I am solving the discrete logarithm problem modulo $N$. $N$ is a composite number, I found its factors — lots of small primes and two big primes ($> 2^{50}$). Does the factorization of $N$ somehow ...
109 views

### Rounds in cryptography

I need to make it clear I know nothing about crypto so in that context I'm hoping to clear up some confusion: As I understand it a "round" in a cipher is one encryption operation and a cipher like ...
64 views

### Is there an alternative AES schedule?

I'm currently reversing an AES implementation for disk encryption. The odd thing I'm stumbled about is a key schedule where the encryption round keys are not the same as the decryption round keys (in ...
229 views

### Can RSA signing be implemented on top of RSA encryption/decryption?

I need to use RSA-SHA256 signing. Unfortunately not all Microsoft CryptoAPI providers support that. It's possible that I might get a handle to a CryptoAPI provider that can just encrypt/decrypt with ...
281 views

### salsa20 is invertible, useless in CTR mode?

I'm reading the salsa20 spec (sorry for the newbie question, i'm really a newbie here). Every paragraph ends with : "this operation is invertible", I suppose the whole salsa20 algorithm is. If I use ...
From the perspective of a Birthday Paradox attack, isn't it true that CMAC based on AES-128 is weaker than HMAC-SHA-1? The attack on CMAC-AES-128 requires about $2^{64}$ operations whereas the same ...