What is symmetric cryptography?
Symmetric cryptography is an encryption method where the same key is used for both encrypting and decrypting data. It is fast and efficient, and is widely used on the internet and computer systems.
Key Exchange
In symmetric cryptography, it is always necessary to solve how to distribute the key to the parties.
If, for example, Liisa wants to send a message to Jaska, they would meet in advance and agree on an encryption key. However, this is not very convenient, so there are smarter solutions for key exchange in the realm of asymmetric cryptography, which we will cover later in the course!
Two types of symmetric cryptography
Symmetric encryption uses two types of algorithms for encrypting and decrypting data: stream ciphers and block ciphers. Both use the same encryption key, but the amount of data they handle and their operating principles differ from each other.
Virran salausta
- Encrypt the data one bit at a time.
- Uses a key stream encryption, combined with XOR operation, to encrypt plaintext data, producing ciphertext.
- The encryption key is usually a pseudorandom number sequence that is difficult to predict.
Block Cipher
- Encrypt data in fixed-size blocks (e.g. 64 bits).
- The encryption algorithm takes one block at a time and produces a corresponding-sized ciphertext block.
- Often iteration (repetitive application) is used to ensure security.
Bottom line
This is sufficient for now! Next, let's continue to explore block ciphers in more detail.
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