Anonymous transactions with blind signatures

[xekoukou]

(With the blind signature implementation I have in mind, this doesnt work inside stellar, rather it works as a service from gateways, but I am putting it here, because someone might find a solution)

Blind signatures is a way to anonymously transfer credit from one account to another when both accounts trust the node that has issued the credits.

Stellar needs to implement the blind signature scheme for this to work.

How does a blind signature work?

Let U,Ua, Tu, where U is the user account that trusts Tu and Ua is the anonymous account of the user that trusts Tu.

An anonymous transfer from U to Ua happens in this way:
Ua requests a deposit slip of a sum X from stellar.
The stellar network encrypts a unique random number R and sends it to Ua.
Ua gives it to U.
U multiplies it with a specific type of random number and blinds it.
U sends it to stellar.
The ledger removes X credit from the U account and signs the blind deposit slip.
U knows R.
U gives R to Ua.
Ua gives R to stellar and the stellar ledge adds X credit to the Ua account.

For technical information, look at this: https://en.wikipedia.org/wiki/Anonymous_Internet_banking

How can one perform an anonymous transaction with blind signatures?

Let S, Sa, Ts, where S is the sender account that trusts Ts and Sa is the anonymous account of the sender that trusts Ts.
Let R, Ra, Tr, where R is the receiver account that trusts Tr and Ra is the anonymous account of the sender that trusts Tr.

The sender sends anonymously credit from S to Sa.
The sender uses the stellar network to transfer credit to the Ba account.
The recipient sends anonymously credit from Ba to B.

[codeck]

the proposing protocol update is related.
stellar/stellar-core#846 stellar/stellar-core#965

[Ratniex]

@xekoukou Where does the network get the number R? If network creates it then it is public.

[xekoukou]

@Ratniex Sorry , I do not remember. You can though find information at the wikipedia article.

[theaeolianmachine]

@xekoukou — with both of the referenced stellar core issues closed, is it possible to do this now (I say this only minimally looking at the proposal). Mostly looking to determine what's next — if you're still interested a CAP proposal would be a great way to get this moving.

[xekoukou]

I am currently not working on stellar. You can take over the issue, close it etc.

[theaeolianmachine]

Thanks! Given a lack of activity for some time, will close it out but keep the labels for discoverability for others.