Question

The Pi step function can be written as-

(a) (x, y) × (y, (x + y))

(b) (x, y) × (y, (2x + 3y))

(c) (x, 2y) × (y, (2x + 3y))

(d) (x, 2y) × (y, (x + y))

The question was asked at a job interview.

My enquiry is from Secure Hash Algorithms (SHA) in portion Other Public Key Cryptosystems and Cryptographic Hash Functions of Cryptograph & Network Security

Answer 1

The correct option is (b) (x, y) × (y, (2x + 3y))

To explain I would say: The Pi function is represented as (x, y) × (y, (2x + 3y)) in terms of matrix multiplication.