Introduction to Cryptography
Symmetric key cryptography is a type of cryptography that uses the same key for both encryption and decryption. This means that both the sender and the receiver of a message use the same key to transform the plaintext into cipher text and back again. Symmetric key cryptography is also known as secret key cryptography because the key used to encrypt and decrypt the message must be kept secret. If the key falls into the hands of an unauthorized person, they can easily decrypt the message and read its contents.
One of the most common examples of symmetric key cryptography is the Advanced Encryption Standard (AES). AES uses a block cipher algorithm that encrypts data in fixed-size blocks. The size of the block used depends on the key size. For example, a 128-bit key will encrypt data in 128-bit blocks.
Another important aspect of symmetric key cryptography is key distribution. In order for two parties to communicate using symmetric key cryptography, they must first share the secret key. This can be done by physically exchanging the key, or by using a secure key exchange protocol. However, this can be a challenge when communicating over insecure channels such as the internet.
Despite its limitations, symmetric key cryptography is still widely used in modern cryptography. It is fast and efficient, and can be used to encrypt large amounts of data quickly. However, it is important to ensure that the key used is kept secret and secure to prevent unauthorized access to the encrypted data.
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