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We've had theoretically-unbreakable cryptography for a long time now, particularly hash functions and encryption ciphers. There are still some weaknesses around

We've had theoretically-unbreakable cryptography for a long time now, particularly hash functions and encryption ciphers. There are still some weaknesses around timing attacks, and of course there's always the "wrench attack," but the algorithms themselves are as secure as we will ever need anything to be.

schoen 4y ago
None of our block cipher or hash function primitives have unconditional security proofs; a lot of the reason to accept them is that the best-known attacks against the widely-used ones are very poor, even after a lot of knowledgeable people have studied them for a long time. But that doesn't logically exclude the possibility that there are unknown mathematical insights that would lead to much more effective attacks. Often, protocols or constructions on top of these cryptographic primitives may have proofs that unconditionally reduce their security to the security of the primitives ("breaking this is at least as hard as AES", normally because "if you could break this, you could also break AES"), or in some cases proofs that do this by making only comparatively uncontroversial mathematical assumptions. This is a good situation to be in, all things considered, and way better than the past, but it's not an ideal situation!
zeroonetwothree 4y ago
Outside of OTP no encryption is “theoretically unbreakable”. They all rely on unproven assumptions.
- MattPalmer1086 4y ago
  I'd go so far as to say that outside OTP, cryptography is always breakable. You can always just guess keys. The aim of most secret key cryptography is to make sure there aren't much better strategies than that to break it, or if there are that the key sizes are sufficiently big it doesn't matter. With OTP you can't guess keys, as there is a valid key for any possible message. It is unbreakable without the original key.
benibela 4y ago
There is no proof that hash functions exist

schoen 4y ago

None of our block cipher or hash function primitives have unconditional security proofs; a lot of the reason to accept them is that the best-known attacks against the widely-used ones are very poor, even after a lot of knowledgeable people have studied them for a long time. But that doesn't logically exclude the possibility that there are unknown mathematical insights that would lead to much more effective attacks. Often, protocols or constructions on top of these cryptographic primitives may have proofs that unconditionally reduce their security to the security of the primitives ("breaking this is at least as hard as AES", normally because "if you could break this, you could also break AES"), or in some cases proofs that do this by making only comparatively uncontroversial mathematical assumptions. This is a good situation to be in, all things considered, and way better than the past, but it's not an ideal situation!

zeroonetwothree 4y ago

Outside of OTP no encryption is “theoretically unbreakable”. They all rely on unproven assumptions.

MattPalmer1086 4y ago
I'd go so far as to say that outside OTP, cryptography is always breakable. You can always just guess keys. The aim of most secret key cryptography is to make sure there aren't much better strategies than that to break it, or if there are that the key sizes are sufficiently big it doesn't matter. With OTP you can't guess keys, as there is a valid key for any possible message. It is unbreakable without the original key.

benibela 4y ago

There is no proof that hash functions exist