IDEA in 448 bytes of 80x86

By Fauzan Mirza <>
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Idea is a symmetric key block cypher. Key sizes are 128 bits, and IDEA is believed to be stronger than both DES (56 bit keys) and triple-DES sometimes denoted "3DES" (112 bit keys).

IDEA also has the distinction of being the conventional cypher used in PGP in conjuction with the RSA public key algorithm.

There is one other feature of tiny IDEA. Because of the way CFB works, it doesn't need a decryption key (technically, tiny IDEA doesn't have an IDEAinvertkey function). This means whichever option you choose (+ or -) it will be encrypting your file; it's just that you need to choose the other option to reverse the operation.

There are a couple of problems with the tiny IDEA program:

If you encrypt a file and forget your password, don't ever expect to recover your file unless you work for the NSA and don't mind letting a couple of Crays try brute force on it for a couple of million years.

Technical details about the tiny IDEA program

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