Decrypt the message that was encrypted using RSA algorithm with
and
.
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Decrypt the message that was encrypted using RSA algorithm with
and
.
Alice wants to use the ElGamal digital signature scheme with public parameters ,
, secret value
and
. She wants to sign the message
and send it to Bob. She chooses
as the secret value. Explain the procedure that Alice will use for computing the signature of the message. What information will she send Bob?
Decrypt the ciphertext 101000111001 which was encrypted with the Toy block cipher once using the key 101010010. Show all the steps.
b) A 64 bit key for the DES is given below 11000111
10000101
11110111
11000001
11111011
10101011
10011101
10010001
i) Check whether the key is error free using the parity bits.
Decrypt each of the following cipher texts:
i) Text: "CBBGYAEBBFZCFEPXYAEBB", encrypted with affine cipher with key (7,2).
ii) Text:"KSTYZKESLNZUV", encrypted with Vigenère cipher with key "RESULT".
b) Another version of the columnar transposition cipher is the cipher using a key word. In this cipher, we encrypt as follows: Given a key word, we remove all the duplicate characters in the key word. For example, if the key word is ‘SECRET’, we remove the second ‘E’ and use ‘SECRT’ as the key word. To encrypt, we form a table as follows: In the first row, we write down the key word. In the following rows, we write the plaintext. Suppose we want to encrypt the text ‘ATTACKATDAWN’. We make a table as follows:
| S | E | C | R | T |
| A | T | T | A | C |
| K | A | T | D | A |
| W | N | X | X | X |
Apply the frequency test, serial test and autocorrelation test to the following sequence at level of significance :
011001110000110010011100.
Alice wants to send Bob the message . She chooses
. How will she compute the cipher text? What information does she send to Bob?
Bob uses ElGamal cryptosystem with parameters ,
and the secret value
. What values will he make public?