Quote from: terrabyte on February 23, 2017, 07:43:10 AM

Is it true that all of the full hex private keys are 64 hex characters long?

I have a friend that wrote down a private key years ago on a piece of paper. Unfortunately, he was messy on a few spots, and there's a hole on one of the characters, etc. I have written a program that will spit out all the possible combinations, then computed the corresponding WIF & public addresses, and then check the address for activity and balance.

In this case, the original private key combinations are ranging from 61 to 65 characters long. It would be nice to narrow down the combinations if I can safely discard the non-64 length ones.

(The reason I'm having a hard time being sure, is because you would be surprised what little shows up in my searches. Almost all talk about private keys starts with either compressed or the Base58 WIF Key. What little talk there is about the hex private key often mention 65 characters. I believe that's because of the prefix character added for computation. Also, when using bitaddress.org page for testing, even though an error pops up saying a 61 or 65 character private key is invalid, it then goes ahead and shows the results of the public address. For the 61-63 character addresses, it seems to be prefixing zeros to make it 64 characters long. Not sure how he computed the 65 length ones)

Thank you for setting me straight!

Check out these for more information:
http://bitcoin.stackexchange.com/questions/2013/why-does-the-length-of-a-bitcoin-key-vary
And
https://en.bitcoin.it/wiki/Private_key