Information-theoretic security (also known as unconditional security) is a type of cryptographic security that is based on mathematical principles rather than computational complexity. In information-theoretic security, it is proven that an attacker with infinite computational power cannot break the encryption, rather than relying on the fact that the encryption is too difficult to break with current computing technology.
One example of information-theoretic security is the one-time pad. The one-time pad is a simple encryption scheme that provides perfect secrecy, meaning that it is mathematically impossible for an attacker to determine the plaintext from the ciphertext, even with infinite computing power. The one-time pad is based on the principle of XOR (exclusive or) operations and uses a truly random key that is as long as the message being encrypted.
In this script, the xor_bytes function performs the XOR operation between two bytes objects. The generate_key function generates a random key of the same length as the plaintext. The encrypt function encrypts the plaintext using the XOR operation with the key, and the decrypt function decrypts the ciphertext using the same key and XOR operation. Finally, the script generates a random key and uses it to encrypt and decrypt the message "Hello, world!" and prints the results to the console.
Note that the one-time pad is not practical for most use cases because the key must be as long as the message being encrypted and must be truly random, which is difficult to achieve in practice. Additionally, the key can only be used once, hence the name "one-time" pad. However, it is still an interesting example of information-theoretic security.