MATH 456 Midterm: MATH456 ROSENBERG-J SPRING2010 0101 MID EXAM

• School: University of Maryland
• Department: Mathematics
• Course: MATH 456
• Professor: All

Document Summary

The point value of each problem is indicated. The exam is worth a total of 100 points. In problems with multiple parts, whether the parts are related or not, the parts are graded independently of one another. Be sure to go on to subsequent parts even if there is some part you cannot do. L0 and r0 are n bits each) and outputs l2r2, where lj = rj 1, rj = lj 1 kj , j = 1, 2. Here kj, j = 1, 2, are n-bit keys and is xor, bitwise addition. Let a0 be the vector of frequencies of the various letters in english, and let a1, a2, and a3, respectively, be the frequencies of the letters in positions congruent to 1, 2, and 3 mod 3 in the ciphertext. For 0 k 25, let a0,k denote the vector a0 with the entries shifted cyclically by k, so that the rst entry in a0,k is the.