Twitter
Symmetric Encryption work with common keys. However common keys themselves cannot be transported as they are very sensitive. Common keys have to be generated independently by sender and receiver. This is accomplished through key exchange. There are 2 methods to do a Key Exchange. DH(Deffie Hellman), and RSA. As per PCI DSS 1024 bits or more key lengths for DH or RSA is needed. Internet Encryption SSL uses both DH and/or RSA for Key Exchange, to agree on 128 or 256 bit common key (SSL 128 or SSL 256). DH is explained in this presentation. Also explained is AES again.
