How can I test and verify a vanity key before I send coins to it?

Question

I ran vanitygen and oclvanitygen on the same machine, and realized after my run that both exe's share the same output file.

I've had experience in the past where many programs append to the same TXT file that corruption might happen.

Regardless of the source of the corruption, what is the most complete way to validate a key created by vanitygen?

Update

I added the developer tag since I'm looking to do validation in bulk. Command line scripts also work.

Answer 1

If you don't want to do it online, you can try to import the private key into Bitcoin-Qt then see if the matching public key is the one you expected.

Answer 2

Openssl can be used to convert private keys to public keys. The following command gives you the public key from a known private key. The private key should be in the form of a PEM file:

$ cat private_key.pem

-----BEGIN EC PRIVATE KEY-----
MHQCAQEEIMURrYd6CTHlrrV0JOxnze9ldaq3mRYMnYJ8195GldAVoAcGBSuBBAAK
oUQDQgAEANPTV3v+8AMXnIPaerOWziyc6tHbmbhORhbVKv1ACYuO+ohlFaV6QaOz
/AGjoSXV0ZeKxq7FijsAdBzeu23Fgg==
-----END EC PRIVATE KEY-----

Note: if you have a private key in hex format, then you should convert it to PEM format, using the procedure of this answer.

To obtain the public key from the private key we use openssl:

$ openssl ec -pubout /dev/null

-----BEGIN PUBLIC KEY-----
MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAEANPTV3v+8AMXnIPaerOWziyc6tHbmbhO
RhbVKv1ACYuO+ohlFaV6QaOz/AGjoSXV0ZeKxq7FijsAdBzeu23Fgg==
-----END PUBLIC KEY-----

In order to convert a public key to a bitcoin address, we need some steps:

First we need to compute the hash160 of the public key. This can be done as follows:

$ openssl ec -pubout /dev/null |
  openssl ec -pubin -pubout -outform DER 2>/dev/null |
  tail -c 65 |
  openssl dgst -sha256 -binary |
  openssl dgst -rmd160 -binary |
  xxd -p -c 80

ab085c55b735d4a811df3f55e6508634f1ce1e27

Then the hash160 has to be used to calculate the checksum as follows:

$ echo -n "ab085c55b735d4a811df3f55e6508634f1ce1e27" |
  xxd -p -r |
  openssl dgst -sha256 -binary |
  openssl dgst -sha256 -binary |
  xxd -p -c 80 |
  head -c 8

7801f8dc

The hash160, combined with the checksum and with the first byte "00", can be encoded using base 58. This gives us the address:

base58=({1..9} {A..H} {J..N} {P..Z} {a..k} {m..z})

encodeBase58() {
    # 58 = 0x3A
    bc 0) { n%3A ; n/=3A }" |
    tac |
    while read n
    do echo -n ${base58[n]}
    done
}

$ printf "%34s\n" "$(encodeBase58 "00$1$(checksum "$char$1")")" |
  sed "y/ /1/"

1GbLZiNzi7DTB4UowMuyqJw5Bh95yCbu3R

Putting all together, we can use the function publicKeyToAddress, as defined below. This can be part of a bash script, or you can type it on the command line.

base58=({1..9} {A..H} {J..N} {P..Z} {a..k} {m..z})

encodeBase58() {
    # 58 = 0x3A
    bc 0) { n%3A ; n/=3A }" |
    tac |
    while read n
    do echo -n ${base58[n]}
    done
}

checksum() {
    xxd -p -r /dev/null |
    tail -c 65 |
    openssl dgst -sha256 -binary |
    openssl dgst -rmd160 -binary |
    xxd -p -c 80
    )
}

$ openssl ec -pubout /dev/null | publicKeyToAddress

1GbLZiNzi7DTB4UowMuyqJw5Bh95yCbu3R

Answer 3

My best recommendation is to try and import the private key into https://blockchain.info/wallet/ service. This can be found under the advanced tab of the wallet. The corresponding public key will be added into your wallet for deposits.

A second option which does not require and account is to go via https://www.bitaddress.org and parse it with the vanity address tab.

Answer 4

The pycoin Python library could be a good starting point. It has a utility that will give you the public key for a given private key. Unfortunately it doesn't seem to have a command line interface suitable for easy programmatic use.