Symmetric encryption-In symmetric encryption, a single key is used both to encrypt and decrypt traffic.Common symmetric encryption algorithms include DES, 3DES, AES, and RC4. 3DES and AES are commonly used in IPsec and other types of VPNs.
Symmetric encryption algorithms are extremely fast & their relatively low complexity allows for easy implementation in hardware. However, they require that all hosts participating in the encryption have already been configured with the secret key through some external way.
Asymmetric encryption-Asymmetric encryption differs from symmetric encryption primarily in that two keys are used: one for encryption and one for decryption. The most common asymmetric encryption algorithm is RSA.Asymmetric encryptions major strength is its ability to establish a secure channel over a nonsecure medium (for example, the Internet). This is accomplished by the exchange of public keys, which can only be used to encrypt data. The complementary private key, which is never shared, is used to decrypt.