security - What techniques do you use when writing your own cryptography methods? -

for years, maybe 10, i've been fascinated cryptography. read book xor bit-based encryption, , have been hooked ever since thing.

i guess it's more fair i'm fascinated can break various encryption methods, digress.

to point -- methods use when writing cryptography? obfuscation in cryptography?

i use 2 key-based xor encryption, various hashing techniques (sha1) on keys, , simple things such reversing strings here , there, etc.

i'm interested see others think of , try when writing not-so-out-of-the-box encryption method. -- info on how pros go "breaking" various cryptography techniques interesting well.

to clarify -- have no desire use in production code, or code of mine matter. i'm interesting in learning how works through toying around, not reinventing wheel. :)

ian

to contradict else has said far, go it! yeah, code might have buffer overflow vulnerabilities in it, , may slow, buggy, etc, you're doing fun! understand recreational enjoyment found in playing crypto.

that being said, cryptography isn't based on obfuscation @ (or @ least shouldn't be). crypto continue work, once eve has slogged through obfuscated code , understands going on. ie: many newspapers have substitution code puzzles readers try , break on breakfast. if started doing things reversing whole string, yes, it'd harder, joe reader still able break it, neve tuohtiw gnieb dlot.

good crypto based on problems assumed (none proven yet, afaik) difficult. examples of include factoring primes, finding log, or other np-complete problem.

[edit: snap, neither of proven np-complete. they're unproven, yet different. still see point: crypto based on one-way functions. operations easy do, hard undo. ie multiply 2 numbers vs find prime factors of product. catch tduehr]

more power playing around cool branch of mathematics, remember crypto based on things hard, not complicated. many crypto algorithms, once understand them, mindbogglingly simple, still work because they're based on hard, not switching letters around.

note: being said, algorithms add in quirks (like string seversal) make brute forcing them more difficult. part of me feels read somewhere referencing des, don't believe it... [edit: right, see 5th paragraph of article reference permutations useless.]

btw: if haven't found before, i'd guess tea/xtea/xxtea series of algorithms of interest.