Affine Cipher. Assume that a = 15 and b = 12 in affine cipher. What is the
Question:
Affine Cipher.
Assume that a = 15 and b = 12 in affine cipher. What is the encryption of 8, 11, and 13 (e(8), e(11), e(13))? What is the decryption of 8, 11, and 13 (d(8), d(11), d(13))?
An obvious approach to increase the security of a symmetric algorithm is to apply the same cipher twice, i.e.: y = ek2(ek1(x))
As is often the case in cryptography, things are very tricky and results are often different from the expected and/ or desired ones. In this problem we show that a double encryption with the affine cipher is only as secure as single encryption! Assume two affine ciphers ek1 = a1x+b1 and ek2 = a2x+b2. Show that there is a single affine cipher ek3 = a3x+b3 which performs exactly the same encryption (and decryption) as the combination ek2(ek1(x)). Find the values for a3, b3 when a1 = 11, b1 = 8 and a2 = 17, b2 = 12.
An Introduction to Management Science Quantitative Approaches to Decision Making
ISBN: 978-1111823610
14th edition
Authors: David R. Anderson, Dennis J. Sweeney, Thomas A. Williams, Jeffrey D. Camm, James J. Cochran