MATH 456 Midterm: MATH456 ROSENBERG-J SPRING2013 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. Simple calculators are allowed: (20 points total) a hill-style cipher works as follows. The plaintext, written as a sequence of bits, is broken into 3-bit blocks, each thought of as a length-3 vector with entries in z/2 (the integers mod 2). A block x is then encoded to another 3-bit block via the map x 7 xa, where a is an invertible 3 3 matrix with entries that are integers mod 2. Find the length n of k. (b) (10 points) if k1 = key and k2 = chain, nd k. you can use this table of numerical equivalents: a.