Ann was very keen to know the contents of the report written by her supervisor about...

 

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Ann was very keen to know the contents of the report written by her supervisor about her performance. The supervisor had sent the report to John, the head of HR, by email. Luckily Ann was able to intercept the email and get hold of a copy of the report. Unfortunately for Ann, the file was encrypted using the public key of John. She thinks it would be possible to recover the plain text of the original message from the intercepted ciphertext C generated using the RSA algorithm provided that John would sign a single message created by Ann (encrypt with his private key). John has already received the encrypted report so Ann cannot send the cipher text directly and expect John to decrypt it and send it back. This is what Ann has decided to do: She chooses a random value r, which is less than n (r < n) and computes the following values: Z = r" mod n T = Z x C mod n Y =r mod n (which is equivalent to Y xr mod n = 1, that is Y is the multiplicative inverse of r modulo n). Now Ann gets John to encrypt T with his private key (d) under the pretence that she wants to verify whether John's public key works. John accepts Ann's request and returns X Td mod n as the reply. With the above information, Ann thinks that she can get the original message M (M = Cd mod n). Do you think that she will be successful in her crypto analysis. You must first clearly state yes she will succeed or no she will fail in recovering the message. Then you must explain why in either case. Ann was very keen to know the contents of the report written by her supervisor about her performance. The supervisor had sent the report to John, the head of HR, by email. Luckily Ann was able to intercept the email and get hold of a copy of the report. Unfortunately for Ann, the file was encrypted using the public key of John. She thinks it would be possible to recover the plain text of the original message from the intercepted ciphertext C generated using the RSA algorithm provided that John would sign a single message created by Ann (encrypt with his private key). John has already received the encrypted report so Ann cannot send the cipher text directly and expect John to decrypt it and send it back. This is what Ann has decided to do: She chooses a random value r, which is less than n (r < n) and computes the following values: Z = r" mod n T = Z x C mod n Y =r mod n (which is equivalent to Y xr mod n = 1, that is Y is the multiplicative inverse of r modulo n). Now Ann gets John to encrypt T with his private key (d) under the pretence that she wants to verify whether John's public key works. John accepts Ann's request and returns X Td mod n as the reply. With the above information, Ann thinks that she can get the original message M (M = Cd mod n). Do you think that she will be successful in her crypto analysis. You must first clearly state yes she will succeed or no she will fail in recovering the message. Then you must explain why in either case.

Answer rating: 100% (QA)

Required solution Answer Yes Ann can retrieve the m... View the full answer