[OTR-users] otr modify toolkit

[Bjorn Kuiper]

> -----Oorspronkelijk bericht-----
> Van: otr-users-bounces at lists.cypherpunks.ca [mailto:otr-users-
> bounces at lists.cypherpunks.ca] Namens Ian Goldberg
> Verzonden: Thursday, July 2, 2015 2:13 PM
> Aan: otr-users at lists.cypherpunks.ca
> Onderwerp: Re: [OTR-users] otr modify toolkit
> 
> On Tue, Jun 30, 2015 at 02:03:59AM +0200, Bjorn Kuiper wrote:
> > > > Wouldn't the mackey be the key that I can retrieve using
> > > > otr_parse,
> > thus:
> > > > 8dfd40e19d32e778410200de0235a5787e294216 ?
> > >
> > > No, that's the MAC tag, not the MAC key.
> > >
> > > > Or would it be the mackey that I would retrieve when
> > > > re-establishing a new DH key and get it from the list of old
mackeys?
> > >
> > > Indeed.  There are two ways to get the MAC key.  One is if you know
> > > the private part of a DH key, in which case you can use otr_sesskeys
> > > to get
> > it.
> > > The other is if you have a transcripts containing later messages
> > > that
> > contain
> > > this key as an "old mackey", which you get with otr_parse.
> > >
> > >    - Ian
> >
> > So consider the attached private key pidgin file, the private key of
> > __bob would be "2E3342837ACFB215EF502845CB48BB724762B950"
> 
> You can't find the private DH key in any file; that would defeat the
forward
> secrecy property of OTR.  You've got the private DSA key there instead.
> 

Thank you. I got it working. Here is a working example.

Message: hi alice
Encrypted message:
?OTR:AAIDAAAAAAEAAAABAAAAwDjO4gildvUsAA5n4+BJhGnJBj+PzS6RUhWxyY9OL/7juxInO1e
Aq6yxb5WmFnsP0CTezw3t0iekfQJ2o8s9bmi6ON72TEYSCRJJUkR3mhtGP0sm5G67sSvmLOIEJ0n
RKDZFN3wpYE29I4qNEzsph620KsOsOiaCG8+8GYXa4o7jlPHE0HAKgxUg/XkbrCFEAsqBFEMzLRW
jusTuhFY1jZCaBUcgheA5cSfzG0iNLmeTroZ3VjQVfM79RUh4HClVdwAAAAAAAAABAAAACX9Ka0E
QUka5WtEBF4hzVyBKG4cupxdEoqB/JxsiAAAAAA==.

Revealed MAC key: 99ed1ef9b0a5f4c6755fbd9a1271064a71ce2ce5

Using otr_modify
$ ./otr_modify.exe  99ed1ef9b0a5f4c6755fbd9a1271064a71ce2ce5 alice bjorn 3
?OTR:AAIDAAAAAAEAAAABAAAAwDjO4gildvUsAA5n4+BJhGnJBj+PzS6RUhWxyY9OL/7juxInO1e
Aq6yxb5WmFnsP0CTezw3t0iekfQJ2o8s9bmi6ON72TEYSCRJJUkR3mhtGP0sm5G67sSvmLOIEJ0n
RKDZFN3wpYE29I4qNEzsph620KsOsOiaCG8+8GYXa4o7jlPHE0HAKgxUg/XkbrCFEAsqBFEMzLRW
jusTuhFY1jZCaBUcgheA5cSfzG0iNLmeTroZ3VjQVfM79RUh4HClVdwAAAAAAAAABAAAACX9Ka0E
QUka5WtEBF4hzVyBKG4cupxdEoqB/JxsiAAAAAA==.
?OTR:AAIDAAAAAAEAAAABAAAAwDjO4gildvUsAA5n4+BJhGnJBj+PzS6RUhWxyY9OL/7juxInO1e
Aq6yxb5WmFnsP0CTezw3t0iekfQJ2o8s9bmi6ON72TEYSCRJJUkR3mhtGP0sm5G67sSvmLOIEJ0n
RKDZFN3wpYE29I4qNEzsph620KsOsOiaCG8+8GYXa4o7jlPHE0HAKgxUg/XkbrCFEAsqBFEMzLRW
jusTuhFY1jZCaBUcgheA5cSfzG0iNLmeTroZ3VjQVfM79RUh4HClVdwAAAAAAAAABAAAACX9Ka0I
WVFeyWhnnXhTcl/k1RH2crMBk21qimPfSAAAAAA==.

Greetings Bjorn