Chapter 1: Q22E (page 49)
Prove or disprove: If a has an inverse modulo b, then b has an inverse modulo a.
Short Answer
Yes, It can be proved that ifa has an inverse modulo b, then has an inverse modulo a.
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Chapter 1: Q22E (page 49)
Prove or disprove: If a has an inverse modulo b, then b has an inverse modulo a.
Yes, It can be proved that ifa has an inverse modulo b, then has an inverse modulo a.
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In an RSA cryptosystem, p = 7and q = 11(as in Figure 1.9). Find appropriate exponents and .
In the RSA cryptosystem, Alice’s public key is available to everyone. Suppose that her private key d is compromised and becomes known to Eve. Show that if (a common choice) then Eve can efficiently factor N.
On page 38, we claimed that since about a fraction of n-bit numbers are prime, on average it is sufficient to draw random n -bit numbers before hitting a prime. We now justify this rigorously. Suppose a particular coin has a probability p of coming up heads. How many times must you toss it, on average, before it comes up heads? (Hint: Method 1: start by showing that the correct expression is . Method 2: if E is the average number of coin tosses, show that ).
Alice and her three friends are all users of the RSA cryptosystem. Her friends have public keys where as always, for randomly chosen n-bit primes . Showthat if Alice sends the same n-bit message M (encrypted using RSA) to each of her friends, then anyone who intercepts all three encrypted messages will be able to efficiently recover M.
(Hint: It helps to have solved problem 1.37 first.)
The Fibonacci numbers are given by the recurrence. Show that for any.
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