Large Twin Primes
There may well be only few twin prime pairs with 100 digits known - I didn't exhaustively follow all the links - I figured, if you were interested, you'd do that. There was a list of thet first 100,000 twin pairs (and I don't think they got anywhere near 100 digits) on one site.. and some gzip'ed files with lots of numbers in them. Sadly I didn't see a twin prime checking machine. (Aren't twin primes bad for RSA? A naive division algorithm might start at the square root of the number to be factored and hit the answer in two steps or so - I just remember a question like that appearing on a computer project once - explain why primes close together are not as good as primes far apart in RSA. Of course this was something I read once 4 years ago and I could be misremembering).