/Cryptography

Primary LanguagePython

Cryptography

Welcome to the Cryptography project! In this project, you will implement programs to perform public-key encryption, compute cryptographic checksums (keyless and keyed), and verify the integrity of files using these checksums.

Section 1: Public-key encryption

  1. Create a file called sensitive.txt in the current directory.

  2. Write a program called generate_keys that generates a pair of 3072-bit RSA keys and saves the public key to a file called pub_key and the private key to a file called priv_key.

To run the program, open a terminal window and type generate_keys. Then, display the contents of pub_key and priv_key using the hexdump command.

  1. Write a program called encrypt_file that encrypts the contents of sensitive.txt using the public key in pub_key. The encrypted file will overwrite the original sensitive.txt. Make sure that the original (unencrypted) sensitive.txt is in the same directory as the program.

To run the program, open a terminal window and type encrypt_file. Then, display the first 100 bytes of the encrypted sensitive.txt using the hexdump command.

  1. Write a program called decrypt_file that decrypts the contents of sensitive.txt using the private key in priv_key. The decrypted file will overwrite the encrypted sensitive.txt. Make sure that the encrypted sensitive.txt is in the same directory as the program.

To run the program, open a terminal window and type decrypt_file. Then, display the first 100 bytes of the decrypted sensitive.txt using the head command.

Section 2: Cryptographic checksums

  1. Write a program called compute_checksum that computes a keyless cryptographic checksum of sensitive.txt using the SHA256 hash function. The checksum should be written to a file called sensitive_checksum.txt in text format.

Display the checksum of sensitive_checksum.txt using the cat command.

  1. Write a program called verify_checksum that computes a checksum of sensitive.txt using SHA256 and compares it with the contents of sensitive_checksum.txt. If the resulting hash values are the same, the program should output "Accept!" and otherwise it should output "Reject!".

  2. Write a program called compute_keyed_checksum that works similarly to compute_checksum, but instead of SHA256, it should use the keyed hash function HMAC-SHA256. A 256-bit key should be read from a file called key.bin. The checksum should be written to a file called sensitive_keyed_checksum.txt in text format.

The file key.bin can be created using the command head -c 256 /dev/urandom > key.bin

Display the checksum of sensitive_keyed_checksum.txt using the cat command.

  1. Write a program called verify_keyed_checksum that works similarly to verify_checksum, but it should compute a keyed checksum of sensitive.txt using HMAC-SHA256 and compare it with the contents of sensitive_keyed_checksum.txt. If the resulting values are the same, the program should output "Accept!" and otherwise it should output "Reject!".