Question: Alice received the following ciphertext from Bob, 0 8 1 4 0 8 . Bob had encrypted it using the RSA cypher with

Alice received the following ciphertext from Bob, "081408". Bob had encrypted it using the RSA cypher with Alice's public key
(pq, e)=(55,3),
where
p =5
and
q =11.
Note that
(p 1)(q 1)=40.
The value for d in Alice's private key,
(pq, d)
is a positive inverse for
3 modulo (p 1)(q 1).
It was found to be 27 in Example 8.4.8(b) and Example 8.4.10. What is Bob's message after Alice decrypts it?(Assume Bob encoded one letter at a time using the encoding
A =01, B =02, C =03,, Z =26.)
To decrypt Bob's message, Alice uses the decryption formula
M = C mod ,
where M is the code for a letter of the message, C is the encrypted version of the letter,
(pq, e)=(55,3)
is the public key, and
(pq, d)=(55,27)
is the private key.
(a)
To begin, Alice computes the values of
a, b, c, d and e
that are indicated below.
081a (mod 55)082 b (mod 55)084 c (mod 55)
088d (mod 55)0816 e (mod 55)
She finds that
a =,
b =,
c =,
d =,
and
e =.
Because
27=16+8+2+1,0827=0816+8+2+1=0816088082081,
she uses the values of
a, b, d, and e
to compute
0827 mod 55=(a b d e) mod 55=.
Thus, the first letter in Bob's message is .
(b)
Alice finds the second letter of Bob's message by computing
27 mod 55=.
(c)
What is Bob's message after Alice finishes decrypting it?

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