For spotting transactions to which you have the stealth key (or at least the
scan key) and creating transactions to a stealth address. So far it is only
partially working - you can see if a transaction is a stealth transaction (or
at least one of a limited kind of stealth transactions), and you can see that
you do not have the stealth key to spend one of these transactions. However, I
have not yet tested whether you can see a stealth transaction that you actually
have the key to. Also, it is not yet easy to spend to a stealth address.
These functions are prefixed DW which stands for Dark Wallet. The code for the
Dark Wallet address format can be found here:
https://github.com/darkwallet/darkwallet/blob/develop/js/util/stealth.js
Note that I deliberately support only the simplest possible format, which is
where there is only one payload pubkey and the prefix is blank. I should now go
back and replace my old toString, fromString, toBuffer, fromBuffer functions
with these Dark Wallet versions, since they are much more well-thought out than
mine.
I had been using this formula for the receiveKeypair:
scanKeypair + payloadKeypair + sharedKeypair
However, Dark Wallet uses this formula:
payloadKeypair + sharedKeypair
It is not actually necessary to add the scanKeypair in order to have all the
features of stealth addresses, at least as far as I can tell. So in order to
bring my implementation closer to Dark Wallet's, I have removed the scanKeypair
from this calculation.
It should be possible to check to see if a message isForMe with only the
scanKeypair, and not the payloadKeypair. There was a bug where only the
scanKeypair was being used to produce the receiveKeypair, but this was a
mistake. Both the scanPubkey and payloadPubkey should be necessary to produce
the receivePubkey, and both the scanPrivkey and payloadPrivkey should be
necessary to produce the receivePrivkey. If an online computer has only the
public keys of both (and the scanPrivkey), then that is good enough to check
for isForMe.
This code should be regarded as being a proof-of-concept, and needs more review
before being used in production code. At least one thing is guaranteed to
change, and that is the format of a stealth address.
"Keypair" is a more explanatory name, and also should be less confused with
other kinds of keys (particularly "cipher keys", which are the keys used in
symmetric block ciphers, especially AES).
This is more explanatory ("symmetric encryption") and also does not encourage
its use for people who don't know what they're doing. (It should only be used
in combination with some type of message authentication.)
This is a standard algorithm for the purposes of padding a block for a block
cipher. It will be used in CBC, which in turned will be used with AES for
ECIES.
Ryan X. Charles
Ryan X. Charles