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Unformatted text preview: (1.1) (1.1) p.192 #4. Decryption is done by modular exponentiation, raising the encrypted message c to the 67 power, mod 101. with(numtheory): phi(101); d=1/3 mod phi(101); 100 p.192 #7. If d is the decryption exponent, then mod n, so Eve can then find the message by dividing by 2. Since for a number written in binary, division by 2 is effected by shifting the number one place to the right, division by 2 is particularly easy to do. p.192 #8. There is no increase in security my double encrypting using RSA. (That is not the situation with some other encryption schemes. For example, when the Data Encryption Standard became too weak, as computing power increased, Triple encryption with DES, or "Triple DES" became the standard replacement until the selection of the Advanced Encryption Standard.) , so double encryption effectively only changes the encryption exponent. Since the security of the system relies on the difficult in factoring n, not the choice of encryption exponent, then no additional security arises, provided both encryption exponents are properly selected in the first place.arises, provided both encryption exponents are properly selected in the first place....
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- Spring '08