I think this is really tough question, but lets try.
I'm implementing small software in J2ME environment. Part of that software is to encrypt a small txt-file using a password based encryption. I'm using SATSA (Security And Trusted Services API, JSR177) for actual encryption. However, I need to generate a key for that encryption process. Key generation must be done using so called "slow funcktion". I have decided to use PBKDF2 algorithm for that purpose (see: http://www.ietf.org/rfc/rfc2898.txt)
At the moment I have started to implement PBKDF2 for J2ME. I can do everything else, but I have a problem creating PRF (Pseudo Random Function), that is used in key generation process. I can' use Mac and SecretKeySpec classes, that are part of JavaSE:
Donald Knuth defines a PRF algorithm in his seminal work "The Art of Computer Programming". Basically, it chops the preceeding number in the series into 2 parts, then merges the parts using simple arithmetic.
You should be able to google for Random Number Generator Algorithm and find lots of code.
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