If an attacker got cipher text c how would they crack 1) openssl encrypted file 2) GPG encrypted email 3) truecrypt file assuming they do not have the private key or the symmetric password? I know the crypto for dummies answer in some of these examples is "well they would brute force it duh"...

In the Diffie-Hellman key exchange, one of the steps involves calculating a primitive root of a prime number $p$. How would one go about doing so, considering that $p$ could be very large? Is there some sort of algorithm or equation? (if this question belongs on Math.SE, please move it there)

I was looking at foaf+ssl http://www.w3.org/wiki/Foaf+ssl and wondering if its possible to spoof the modulus of the browser cert so that the foaf and browser cert modulus match

Due to a number of recently asked questions about Diffie-Hellman, I was thinking this morning: must $g$ in Diffie-Hellman be a generator? Recall the mathematics of Diffie-Hellman: Given public parameters $p$ (a large prime) and $g$ (always referred to as a generator of $\mathbb{Z}_p$). Alice ...

I understand that signing is often a case of hashing data and then encrypting the hash with the private key. What properties keep Diffie-Hellman from being useful for this?

So, I have an idea... this is based partly on the fact that certain things such as book lists and subjective discussion aren't great fits for the SE engine (although communities have been known to make it work. You can debate that issue here. So my thought was - why don't we make use of the cryp...

I'm using PHP to encrypt a string and Java to decrypt it on a remote server. To perform the encryption, I'm using the following strategy: http://www.logikdev.com/2010/11/01/encrypt-with-php-decrypt-with-java/ My problem is that the strings I encrypt are pretty small and very similar each other...

My understanding of HOTP is that each password is unique and based on a counter. $$PASSWORD = HOTP_1(K,C)$$ Where $C$ is an incremental counter. What I wish to know, is how you keep the client and server in sync? Looking at current systems (google authenticator), there appears to be no indi...

I, myself, do not plan on getting into a situation where I would be unable to use a computer in order to communicate securely. However, I can think of many practical situations in which mental cryptography would be useful. Is there a secure cryptosystem that is simple enough to be performed men...