Fifteen-year-old Peter Schmidt-Nielsen spent only a month working on his submission, but he thinks he's come up with something "unusual and new." Never mind that he's up against some of the most famous cryptographers in the world.

Schmidt-Nielsen is one of more than 60 entrants in what's expected to be a four-year contest to pick a new hashing algorithm that will help lock down the cryptography used by everything from Web-based payment systems to secure e-mail to source-code management tools.

The contest, sponsored by the National Institute of Standards and Technology (NIST), hopes to find a new cryptographic hash algorithm to replace the SHA-2 (Secure Hash Algorithm - 2) algorithm that NIST published eight years ago. The deadline for SHA-3 submissions was Oct. 31, and NIST hopes to cut the field down to 15 or 20 contestants by next August. That's when the hard work of hammering away at the submissions and knocking loose any flaws will really begin.

Schmidt-Nielsen and others are doing their work unpaid, competing mainly for prestige and the thrill of seeing their work analyzed by their peers. "I think it's a ton of fun," said Schmidt-Nielsen, who first got into cryptography at the tender age of 13. "It will be really fascinating to watch my algorithm get completely torn apart."

Also in the running are famous cryptographers such as Bruce Schneier, BT's chief security officer, and Ron Rivest, who invented the widely used MD5 hash algorithm.

But what is a hash algorithm anyway?

Hashing is computer talk for finding a way to take a message -- an e-mail, for example -- and representing it with a unique number that appears to be random. Hashing was developed as a way to reduce the computing overhead when programs are doing things like scanning files to see if they've been changed. It's much quicker to compare two hash values than to scan through whole files for changes.

In a cryptographic hash, the number is encrypted, creating a digital signature that can be verified using public key cryptography. In practice, these digital signatures are used to confirm, for example, that a Web site really is the site it claims to be, or that an e-mail message is from the person who claims to have sent it, and that it hasn't been tampered with along the way.

Starting in 2004, researchers led by Shandong University's Wang Xiaoyun found weaknesses in the MD5 and SHA-1 hash algorithms. They discovered that it was easier than had been thought to create two numbers that share the same hash value. In cryptographic parlance this is called a collision, and it's considered a very bad thing because it undermines the integrity of the cryptographic system.