Suppose I have a list of strings where each string is exactly 4 characters long and unique within the list. For each of these strings I want to identify the position of the characters within th...

Our computer system at work requires users to change their password every few weeks, and you cannot have the same password as you had previously. It remembers something like 20 of your last passwor...

I would like to randomly iterate through a range. Each value will be visited only once and all values will eventually be visited. For example: class Array def shuffle ret = dup j = length i = ...

I am given N numbers and for them apply M rules about their order. The rules are represented in a pairs of indexes and every pair (A, B) is telling that the number with index A (A-th number) must b...

How is the encryption algorithm's security dependent on factoring large numbers? For example, I've read on some math-programming forums that by using the Quadratic Sieve or the General Number Fiel...

I'm actually working on a PHP project that will feature a user system (Login,Register,Send lost password to email,..) and I think that this may be very vulnerable to Brute-Force attacks and/or Spam...

I have a mobile application where I would like to store private keys securely. The security requirement implies that it should be very hard for attackers to be able to obtain the private key even i...

A while back I was trying to bruteforce a remote control which sent a 12 bit binary 'key'. The device I made worked, but was very slow as it was trying every combination at about 50 bits per secon...

Recently WiFi encryption was brute forced by using the parellel processing power of the modern GPU. What other real-life problems do you think will benefit from similar techniques?