A digital currency system like Lucre (OpenTransaction) creates a coin by a mint blind signing the output of a hash function, which the payer then unblinds and pairs with the input to the has function. In this way, the coins themselves cannot be used to identify the payer; however, the payee and ...

I need to divide some input (for example, the string helloworldhelloworld) in blocks of 512 bytes, to use it in a cryptography function. But my function needs that the block contains exactly 512 bytes, i.e., if the input is smaller than 512 bytes (or, after breaking it in blocks, the last last b...

There is apparently a provably secure cipher that was proposed by Diffie but enhanced by another cryptographer that works like this: Measure the length of the plain-text, n. Multiply it by 128. Generate this much real random data and split it out in to 128 byte arrays of equal length to the pla...

I am doing an EPQ at school, which is alike an essay at university, although I am struggling to find any books on the matter of cryptography. It is a brief overview on how cryptography (public, private and hash based ciphers) has impacted the economy. What would be the best source of articles o...

From an old exam question: Consider this existential forgery attack on ElGamal. Choose $u$, and $v$ such that $gcd(v, p - 1) = 1$. Compute $r := (y^v g^u mod$ $p)$ (recall that $y := (g^x$ $mod$ $p))$ and $s := (-r(v^{-1})$ $mod (p-1))$ s will be used as part of the forged signature (a) Prov...

http://en.wikipedia.org/wiki/Blom%27s_scheme Another old exam question, I definitely missed the class on this one, because I've never heard of the Blom Scheme. Any other additional information on this would be greatly appreciated! Question: (a) First how can we show that in the Blom Scheme ...

All rounds of AES (and Rijndael) have a MixColumns step, save the last round which omits it. DES has a similar feature where the last round differs slightly. The rationale, if I recall correctly, was to "make the cipher appear similar in reverse as it does in the forward direction." Why does t...