[messaging] Double Ratchet spec

Nadim Kobeissi nadim at nadim.computer
Mon Nov 21 03:26:43 PST 2016

Dear Trevor,
Thank you very much for your diligent work on specifying these important

For the sake of complete clarity, I must ask one final question regarding
this matter:

To my understanding, each of the three components of the Signal protocol
have now been specified in the public domain. Does this mean that a
third-party developer is allowed to combine these three components to
construct a protocol that functions exactly like the full Signal protocol
itself, without that resulting mirror being bound by the GPL license
governing the libsignal libaries, or any other such license or restriction?
Would that third-party developer's resulting library be publishable in the
public domain as well, should that developer desire it?

I have asked this question before these specifications were published, but
did not receive an answer. Now that the specifications are out there in the
public domain, I think it's appropriate for Open Whisper Systems to provide
a clear answer to this query once and for all.

Again, I congratulate you on the accomplishments your team has made towards
making secure messaging more ubiquitous around the world. I hope that with
this public domain approach, more developers will be able to follow in that


On Sun, Nov 20, 2016 at 10:18 PM, Trevor Perrin <trevp at trevp.net> wrote:

> Hi all,
> A spec for the "Double Ratchet" algorithm is available at [1].
> We'd welcome feedback, as usual.
> Trevor
> [1] https://whispersystems.org/docs/
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