Re: light vs quantum

Posted by Dale on Apr 02, 2002 at 19:59

Re: light vs quantum (y)

Actually that is a very good question. Outstanding insight if you really know what you asked. The theoretical answer is not an easy one at all. The code space for an encryption routine could easily exceed the space of the data to be encrypted. A one time pad method (the only known provably unbreakable method) always uses more space since the key is the same size as all the data to be encrypted.

But the practical answer however, is no. Microsoft programs exempted, processors are improving their ability to run code is less memory all the time. Back in the olden days it took an entire subroutine just to add two 32 bit integers. Multiplication was usually a multiple routine set. Today each of these operations can be performed in a single instruction. So as time goes on the amount of needed storage space will not increase and might decrease.

More importantly, the amount of space needed for coding and decoding will always be less than any practical amount of data to be encoded. It seem silly to need more space for the encryption or decryption routine than for the data to be encrypted or decrypted. If you don't have more data than code, why bother with the code? Sort of like buying a new car every time the last one drives far enough to run out of gas. This is the reason the one time pad method is seldom used. The requirement of a key as large as the data makes it too cumbersome except for the highest secrets that must be protected at all costs.

Practically you should be able to develop encryption techniques that outwit the decryption techniques far faster than the new decryption techniques. If you look at the history of encryption, although the complexity has increased, the size of encryption techniques hasn’t gotten much larger in the past 3,000 years. A public key encryption technique can be implemented in a few thousand bytes while a Caesar Cipher takes a few hundred. In other words, we’ve got a long way to go before we run out of memory.

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