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> Since there is a limit to how much data a symmetric cryptographic key can protect Is this regulatory related or self imposed?
by cactusplant7374 2y ago
> Since there is a limit to how much data a symmetric cryptographic key can protect
Is this regulatory related or self imposed?
- tptacek 2y agoNeither: it's because (overgeneralizing) there are bounds on the number of times nonces can be generated under a key without risk of collision, which in AEAD constructions is a devastating event.
- jgalt212 2y agoFor a given nonce collision, how many blocks or messages can be decrypted?
- richardwhiuk 2y agoFor some modes, you can break every message encrypted with that key.
- deleted 2y ago[deleted]
- HeatrayEnjoyer 2y agoBut shouldn't that bound be astronomical?
- stavros 2y agoI'm fairly out of my depth here, but the birthday paradox is a harsh mistress.
- ikiris 2y agoEspecially when the pool of possibilities is equally massive
- tptacek 2y agoGCM is like 4 billion messages, which is not astronomical at Facebook's scale.
- pstoll 2y agoMeta (we) process many billions of messages per second. Finding enough randomness is a thing at scale.
- HeatrayEnjoyer 2y agoPer day? but not per second. would require every human being sending @ message every 8 seconds
- pstoll 2y agoPer second. Messages in the Kafka sense not the WhatsApp sense.
- bdd 2y agoIf you want to read more about cryptographic key wear out, Soatok wrote an excellent explainer on this a few years ago https://soatok.blog/2020/12/24/cryptographic-wear-out-for-symmetric-encryption/ https://soatok.blog/2020/12/24/cryptographic-wear-out-for-sy...