[J65nko]

From http://h-online.com/-1366564

A group calling itself The Hacker's Choice (THC) has released a tool that enables a single computer to disable an encrypting server. The concept used by the tool is based on forcing the server to renegotiate the key used for encryption.

Encrypting and decrypting payload data for services such as https is not particularly resource-hungry. Where an https connection gets really resource-intensive is in establishing the SSL connection, which involves key negotiation. This is, in part, because data encryption is carried out using highly efficient symmetric algorithms such as AES. To negotiate the AES session key, however, SSL needs to use resource-intensive asymmetric algorithms such as RSA. This is due both to the specific mathematical process involved and the key length required – AES, for example, requires 128 or 256 bits, whereas RSA requires 1024 or even 2048 bit keys.