Numberphile recently posted a video about the math behind RSA encryption.  In the video below, a brief description of public key cryptography is given and then we are shown a simple example of the math used to perform encryption and decryption (math example @ 2:25). In the video, James skips over the method for determining the private key, so I thought I would run through the key generation steps for his example. Choose two distinct prime numbers p and q. These are the two primes that he mentioned, so p = 2 and q = 5. Compute n = pq. Simply multiply 2 and 5. n = 10. Compute the totient of n, or (p-1)(q-1). (2-1) times (5-1) is 1[…]

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Dan Kaminsky posted on twitter the following: http://eprint.iacr.org/2010/006.pdf Is it time to deprecate 1024bit RSA for, say, 1276bit? (2048 has perf issues.) The link Dan provided is a research paper which reports the successful factorization of the 768-bit number from the original 2001 RSA challenge. I responded to him that NIST had already deprecated the use of 1024-bit RSA in the government, and it was time for industry to follow suit. Since I posted that, I’ve been surprised that a number of people don’t understand the upcoming changes in key lengths and algorithm strengths that have been mandated by NIST. So, this post offers some information about why I can confidently say the U.S. government has deprecated certain algorithms and[…]