At 09:33 AM 1/18/98 EST, Ryan Lackey wrote:

Documents by specification last only as long as someone is willing to pay to keep them up. This is not necessarily forever.

But it can be, and the costs of doing so aren't much higher than storing it for the first couple of years. Depends on what service the customer wants to buy. And there are applications that require more than 100 years of data protection, e.g. ownership of copyrights which last 50 years beyond the author's death. But for Matt Barrie's question, any permanent document will do.

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Can we assume that using Moore's law this is at least 1 bit every 18 months for symmetric crypto? Do the math, though, for 128bit. There are traditional analyses which include the amount of silicon on the earth, the number of atoms in the universe, etc. The general consensus is that traditional techniques are not feasible for brute forcing 128bit ciphers before the heat death of the universe.

Hard to say. Assuming that Quantum Cryptography doesn't allow finite-sized computers to do large exponentially complex calculations in short finite time, you're probably limited by the number of atoms in the available supply of planets, and Heisenberg may still get you if that's not a low enough limit. Moore's law isn't forever. But there's no particular reason to limit RC4 or RC5 to 128 bits; those are convenient sizes for MD5 hashes of passphrases. So if you're paranoid, use RC4-256 and superencrypt with 5-DES. Thanks! Bill Bill Stewart, bill.stewart@pobox.com PGP Fingerprint D454 E202 CBC8 40BF 3C85 B884 0ABE 4639