| Kerckhoff's principle (1883): a cryptosystem should be secure even if the attacker knows all the details about the system, with the exception of the secret key. |
Modular arithmetic, Rings is used a lot
Most PRNGs, we cannot use in cryptography, instead we need Cryptographically secure PRNGs
paper relating mutual information to longest shared secret established over public channel
Based on the structure of the algorithm, cryptosystem can be classified into two categories, block ciphers and stream ciphers. Block ciphers tend to simultaneously encrypt groups of characters, whereas stream ciphers operate on individual characters of a plaintext message one at a time. In another classification, which is based on the method of distribution of secret key, one classifies cryptosystem into two classes, the symmetric (private) key and the asymmetric (public) key cryptosystems. In a symmetric key cryptosystem, the key used in the decryption process is the same as (or can be easily obtained from) the key used in the encryption process.
Unconditionally secure cipher
Historical ciphers
fully homomorphic encryption: an extremely exciting new class of methods, the rst of which was announced by Gentry [60] in 2009, for performing arbitrary computations on encrypted data without ever decrypting the data. The output of such a computation will look like meaningless gibberish to the person who computed it, but it can nevertheless be understood (and even recognized as the correct output) by someone who knows the decryption key.
What are the implications of pseudorandom generators for the foundations of probability, or of fully homomorphic encryption for debates about the semantic meaning of computations? I very much hope that this essay will inspire others to tackle these and similar questions.
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Bruce Schneier