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January 25, 2017
Who, Not What, is the ‘R’ in RSA?
January 25, 2017
The other day, I took to Cybrary’s search feature in hopes of finding information on an inventor of the RSA public-key cryptosystem, and when nothing turned up, not only was I utterly disappointed, but it made me wonder why we do not dedicate more of our interest to influential individuals within the field of cyber security.It also made me wonder why there are so many ‘household’ names in the general tech industry, but so few it seems, in cyber security specifically.The person I’m referring to, in addition to being an Inventor of the RSA public-key cryptosystem, is also a Founder of RSA Data Security with extensive experience in cryptographic design and cryptanalysis, and has published numerous papers in these areas. Likewise, he has worked extensively in the areas of computer algorithms, machine learning and election integrity.Not too bad of a resume.Know who he is yet? No, okay well more clues.Currently, he’s a Professor at the Massachusetts Institute of Technology and a leader of the Cryptography and Information Security research group within MIT's Computer Science and Artificial Intelligence Laboratory. He received a B.A. in mathematics from Yale University in 1969 and a Ph.D. in computer science from Stanford University in 1974.Give up?This important and accomplished man is Ron Rivest.He, along with Adi Shamir and Len Adleman, are the men behind RSA.Rivest specifically invented the symmetric key encryption algorithms RC2, RC4, RC5. The RC in this case stands for either ‘Rivest Cipher’ or ‘Ron’s Code’ depending on who you ask.RC4 is said to be the world’s most widely used stream cipher.If you’re curious how they work, I’ll give you some insight. But first, vocabulary. A cipher (or cypher) “is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure.”Keystream “is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted message.”Stream cipher “is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream.”Block cipher “is a deterministic algorithm operating on fixed-length groups of bits, called blocks, with an unvarying transformation that is specified by a symmetric key.”Now for the RC ciphers.RC2 is a 64-bit block cipher with a variable size key.RC4 generates a keystream. In order to do so, the cipher makes use of a secret internal state, which consists of two parts:
- A permutation of all 256 possible bytes.
- Two 8-bit index-pointers.