Encryption is the process of converting plaintext into ciphertext using a secret key or algorithm.

Decryption is the process of converting ciphertext back into plaintext using the same secret key or algorithm that was used for encryption.

A cipher is a secret code, a type of encryption algorithm, and a method of hiding data.

Symmetric ciphers are the most common type of cipher and use the same key for encryption and decryption.

Asymmetric ciphers use two different keys, one for encryption and one for decryption, and are more secure than symmetric ciphers. They are also used for digital signatures.

A hash function is a function that converts data of any size into a fixed-size output.

A digital signature is a way to verify the authenticity of a message by using a public key.

A one-time pad is a cipher that uses a key that is the same length as the message and is unbreakable.

AES is the most common type of symmetric cipher and is used in a wide variety of applications.

RSA is the most common type of asymmetric cipher and is used in a wide variety of applications.

SHA-2 is the most common type of hash function and is used in a wide variety of applications.

RSA is the most common type of digital signature algorithm and is used in a wide variety of applications.

The Vernam cipher, OTP, and XOR cipher are all types of one-time pads.

Cryptography is used for a wide variety of applications, including secure communication, data protection, and authentication.

The main challenges in cryptography include developing new algorithms, breaking existing algorithms, and implementing algorithms efficiently.