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Hashed Timelock Agreements (HTLAs)

From: Evan Schwartz <evan@ripple.com>
Date: Wed, 21 Jun 2017 10:09:25 +0000
Message-ID: <CAONA2jW6G0mhZMpqEf4RpDX9nfsWrV9=rCWDDE5qCTHoMUZcBg@mail.gmail.com>
To: Interledger Community Group <public-interledger@w3.org>
What do you think about the term "Hashed Timelock Agreements (HTLAs)"?

An HTLA is a generalization of the idea of a Hashed Timelock Contract
(HTLC), which is the Bitcoin/Lightning Network term for conditional
transfers where the conditions and timeouts are enforced by the ledger.

In Interledger, you don't need all transfers to be enforced by the ledger,
because two parties can treat an unconditional transfer on a ledger or
through a simple payment channel as conditional. Basically, the two parties
are using an agreement based upon a hashlock and a timeout where they say
"if you give me the preimage to the hash before the timeout, I'll send you
the corresponding payment". In that case the recipient takes the risk, but
you could set up the agreement the other way where the sender must send the
amount upfront and the recipient will send the money back if the transfer
times out. Both parties can limit the amount of risk their peer poses
simply by capping the amount they are willing to have unsettled or inflight.

A key point about the security model is that if you use HTLAs to secure
multi-hop transfers (like both Interledger and Lightning do) it's up to
each pair of participants what type of agreement they want to use. If they
have very little trust and their ledger supports more complicated features,
maybe they want to use ledger-enforced HTLCs. If they are friends or have a
business relationship or their ledger doesn't support enforcing HTLCs then
a different type of HTLA would work just fine.

What do you think? Does HTLA get the point across? (If this idea seems
interesting or could use more explanation I could write up a full blog post
about it)
-- 

Evan Schwartz
Software Engineer
Managing Director of Ripple Luxembourg
<http:> <http:>
Received on Wednesday, 21 June 2017 10:10:14 UTC

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