What is the fastest block cipher in the (Intel) world? In AES competition,Rijndael cipher obtained first rank and become Standard and Serpent, Twofish, RC6 and MARS obtained another ranks and I know that Serpent took second rank because it was slower than Rijndael.

My questions are:


Is Rijndael the fastest block cipher in the world?
What is the reason of 10 negative votes for Rijndael in AES2 conference?
What is the fastest block cipher in the world? (for software implementation on Intel processor)


In my question, suppose that I implement all known block ciphers with equality of condition (key size, block size, software implementation on PC) then which secure block cipher is fastest?
The fastest block cipher is identity, which leaves input blocks completely unchanged. This is infinitely fast on all platforms; however, it is not secure. So maybe you want the fastest block cipher that still offers some given non-trivial level of security?

Then it depends a lot on what you want to implement the block cipher on. With recent PC, you would have a hard time getting anything faster than AES, because of specialized opcodes -- although you could define a block cipher that is identical to AES except that it has 9 rounds instead of 10. That alternate block cipher would be faster and still secure, but with less "security margin", an intuitive but very poorly defined notion.

During the AES competition, Rijndael was outperformed on some platforms, e.g. on the PC of that day, RC6 was faster. But Rijndael offered the most consistent performance on platforms of that era: there was no software platform (including 8-bit CPU) were it was abysmally slow, and it was perceived to be reasonably hardware-friendly (contrary to, say, RC6).