The sender and the receiver use the **same secret key and the same cryptographic algorithm** to encrypt and decrypt data. For example, Alice can encrypt a plain text message using her shared secret key and Bob can decrypt the message using the same cryptographic algorithm Alice used and the same shared secret key. The **key needs to be kept secret**, meaning that only Alice and Bob should know it; therefore, **an efficient way for exchanging secret keys over public networks is demanded. ** ![[Pasted image 20230204162649.png]] Popular symmetric algorithms: - [[Advanced Encryption Standard (AES)]] - [[Data Encryption Standard (3DES)]] [[Asymmetric Cryptography (PKC)]] was introduced to **solve the problem of key distribution in symmetric cryptography.** ---- Specific quantum algorithms impact it. However, security can be increased with the use of larger key spaces.