Question

3 Brute Force Attack vs Birthday Attack (50 pts) Message-Digest Algorithm (MD5) and Secure Hash Algorithm 1 (SHA-1) are com- monly used cryptographic hash functions 1. Do research to find the numbers of bits used in MD5 and SHA-1. (8 pts) perform An adversary an attack to a hash algorithm by applying random inputs can and y (y) that satisfie Hx) and repeating until finding two inputs H(y) where H() denotes a hash code. This is called a "hash collision." adversary is trying to find a hash collision using a brute force attack 2. Suppose that an (a) What is the expected number of trials needed to produce a hash collision probability of 0.9 when MD5 is used? (20 pts) produce (b) What is the expected number of trials needed hash collision probability of 0.9 to a when SHA-1 is used? (6 pts) 3. Suppose that an adversary is trying to find a hash collision using a birthday attack (a) What is the expected number of trials needed to produce a hash collision probability of 0.9 when MD5 is used? (8 pts) (b) What is the expected number of trials needed to produce hash collision probability of 0.9 a when SHA-1 is used? (8 pts)

Answer 1

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