密碼學? - 資安

: 除了最原始的凱薩編碼(MAN → PDQ ABC → DEF)&凱撒方格
: 以及Base64
: 還有哪些常見的編碼方式阿??
: ASCII也算是一種嗎@@?

sorry, I can't type in Chinese

密碼學 is cryptography.
編碼 is coding theory.

The purpose and idea is different in many ways

cryptography is trying to hide the information.
coding theory is not to hide information, but to have a way to get back the
information when some noise is introduced.

If we just consider the purpose of ASCII, then ASCII is neither of those.
ASCII is just a mapping from human readable symbols to machine readable
symbols


the idea behind 密碼學 is that some functionality, is easy in one way, but
hard to do in the other way..

for example, RSA depends on factoring 2 primes.
another idea is DLP (discrete log problem), ie, given a, b, and the relation
that a^x = b, how to find x

chen

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