> That's why algorithms got weakened by researchers regularly.

That's the 3rd point. correctness of the algorithms.

There is no such thing. There is just more thorough and less thorough bit-blending. Have a look at any symmetric encryption algorithm or secure hash - there's no magic there, they just do a bunch of stuff to thoroughly mix up all the bits. In the case of symmetric encryption, they constrain it to reversible mixing primitives. And cryptographic experience has shown how much mixing is enough mixing.

A few basic things are known - for example, you can't make a symmetric cipher with just bitshifts and XOR, because then linear algebra techniques can trivially reverse it.

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xboxnolifes 3 days ago | parent [-]

If there is no such thing, how have people found weaknesses in various cryptographic algorithms over the years? The weaknesses are incorrect algorithms.

	▲	tptacek 3 days ago \| parent [-]
		They haven't. Excepting RC4, which is wildly different from every other mainstream cipher, the track record of practical block cipher cryptanalysis (of core algorithms) is meager. If you redesigned DES so that it had 16-byte blocks and keys and the round structure to match, but retained the rest of its core design decisions, it'd presumably be viable (if slow).