Tech Review has put online the 1869 MIT entrance exam. http://libraries.mit.edu/archives/exhibits/exam/arithmetic.html There are 4 parts, English, Arithmetic, Algebra, Geometry. The math parts are relatively easy, corresponding to grade level 10.5, the middle of sophomore year in US high school. I found the English section more challenging: The language skills section is undoable -- the source text to be analyzed is missing. There are questions on history, literature, geography, and current events. I was especially surprised to do badly on the geography questions: I've been to Europe multiple times, and couldn't say exactly where Vienna is, nor describe the course of the Danube. ---- SHA1 update [some funsters have crypto interests] Some respectable cryptographers claim to have reduced the effort to find a SHA1 collision to 2^52 hash computations. Their slides are posted at http://eurocrypt2009rump.cr.yp.to/837a0a8086fa6ca714249409ddfae43d.pdf The presentation is too sketchy to evaluate yet, but the authors are well known. The collision work is about 20 years on a late model PC. ---- Xor Multiply Intel is introducing the PCLMULQDQ instruction, which does a 64x64->128 bit Xor-Multiplication. (Their naming conventions remind me of the Tom Lehrer song about the Red Line.) This instruction is helpful in several crypto applications, and also in working with error correcting codes. Puzzle: a) Use the new instruction in a routine to reverse 64 bits. This swaps the sign bit with the low order bit, etc. b) The new instruction can obviously be used to Xor-Square a 64-bit quantity. Use it to do "square root": collect the odd numbered bits 63-1 in the left half of the word, and the even numbered bits 62-0 in the right half. c) Extra credit: describe the relationship with card shuffling. d) Is PCLMULQDQ useful in implementing an arbitrary pre-specified bit permutation? Rich