A cryptography student has accidentally used the same keystream to encrypt two different messages, M1
and M2
. We know that the ciphertexts are C1=0xb1dcb1e81bb933ee
and C2=0xa36da13ab52d8552
. We also happen to know that M1=0xe7cb99c00c599b7e
.

a) What is M2
in hexadecimal? Please give your answer a leading 0x and use lowercase letters only.
0xf54aa912b3c52fc2
b) What is the keystream? Please give your answer a leading 0x and use lowercase letters only.
0x5627082806e0aa90
Hint: These are all 8 byte numbers and will fit in an unsigned long type on most systems.