Add ability to sign messages to verify ownership of a key

[mflaxman]

Similar to bitcoind

[mflaxman]

Working test code, just needs a UI:

from bitcoin.main import ecdsa_recover, ecdsa_verify, ecdsa_sign

# https://unmitigatedrisk.com/?p=425
msg = '[email protected] – my voice is my passphrase authenticate me'
sig = 'G0d6BnQem1gT4nd9esfsEyn1k/GfYAxDkNJmkNvmz8wCOI2Ncw9DvIcyP7OJcEvWbUHQNIBFK3V8wYdnhEFhYHI='

assert ecdsa_verify(msg=msg, sig=sig, pub=ecdsa_recover(msg=msg, sig=sig))

# http://dev.blockcypher.com/#addresskeychain
privkeyhex = '86751cb880a9a1addcc3b67979976158dd800afe9d14b68349921299b20c94dd'
pubkeyhex = '03866586fbe3652eb219c5ed99c3fc72d125472248183f966e0673be08a1c543de'

sig2 = ecdsa_sign(msg=msg, priv=privkeyhex)

assert ecdsa_verify(msg=msg, sig=sig2, pub=pubkeyhex)

Add verify to block explorer and leave out of wallet