[zeromq-dev] ZeroMQ Curve Publish Subscribe

[LENFERINK Roy]

Hello everyone,

Currently I'm investigating the possibilities of ZeroMQ.

At the moment, I have created a publisher subscribe system with curve enabled.

This is the code I used to get it up and running (got it from Pieter hintjes his blog):
http://pastebin.com/LjV8aKLG

At the moment, the publisher is encrypting data with his private key and
different subscribers can decrypt the data using the publishers public key.
This is more 'authenticating' data than 'encrypting' data.

I would like to swap the keys, so, the publisher should encrypt the data
with his public key, and the subscribers should decrypt the data using
the private key of the publisher.

I have tested it with just loading the public key into the publishers program
and then load the private key into the subscribers program and apply this key to the
subscribers socket, but this is constantly giving me a message:
"CURVE I: cannot open client HELLO - wrong server key?"

Is it possible to use a public key for encrypting data (publisher socket) and
the private key for decrypting data (subscriber socket) with the architecture of ZeroMQ ?

Many thanks in advance,
Roy


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[alex.]

Hi Roy,

it seems you are convoluting how ZeroMQ and CurveMQ work. ZMQ simply
abstracts how clients talk over a network. Pub-Sub is a fine example of
that since you, as a developer can write programs where clients can
fan-out messages, i.e. from one node to many others in one direction.
This does not mean, however, that this is what actually happens. In
fact, ZMQ opens as many (bidirectional) TCP connections between the
publisher and all the subscribers and sends pretty much the same message
from the publisher to all the subscribers, each in its own connection.

What this means for encryption is that the high-level message you send
is actually encrypted with the public key of each subscriber and then
sent individually. In fact, a single subscriber could never decrypt a
message that was sent to another subscriber.

TL;DR it just _seems_ as though the publisher is "encrypting" the
message once with his private key, but in fact the message is encrypted
as many times as there are subscribers.

Cheers!
alex.

Post by LENFERINK Roy
Hello everyone,
Currently I’m investigating the possibilities of ZeroMQ.
At the moment, I have created a publisher subscribe system with curve enabled.
http://pastebin.com/LjV8aKLG
At the moment, the publisher is encrypting data with his private key and
different subscribers can decrypt the data using the publishers public key.
This is more ‘authenticating’ data than ‘encrypting’ data.
I would like to swap the keys, so, the publisher should encrypt the data
with his public key, and the subscribers should decrypt the data using
the private key of the publisher.
I have tested it with just loading the public key into the publishers program
and then load the private key into the subscribers program and apply this key to the
“CURVE I: cannot open client HELLO – wrong server key?”
Is it possible to use a public key for encrypting data (publisher socket) and
the private key for decrypting data (subscriber socket) with the architecture of ZeroMQ ?
Many thanks in advance,
Roy
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Thales Nederland BV is seated in Hengelo and is registered at the Chamber of
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[LENFERINK Roy]

Hi Alex,

Thanks for your answer and explanation. It is now a bit more clear.
I also gave a look on the blogs of Pieter and this private / public key system is for authenticating the subscribers and after you are authenticated some short-term keys are exchanged.
So what I did, I created a .curve directory on my publisher with the public key of the subscriber, and only the subscriber has the private key (and keeps it private).
So now only the subscriber can connect to the socket of the publisher. And then they are securely exchanging the data which will be send between publisher and subscriber.

Thanks!

Greetings,
Roy


-----Original Message-----
From: zeromq-dev [mailto:zeromq-dev-***@lists.zeromq.org] On Behalf Of alex.
Sent: Thursday, 13 October, 2016 17:00
To: zeromq-***@lists.zeromq.org
Subject: Re: [zeromq-dev] ZeroMQ Curve Publish Subscribe

Hi Roy,

it seems you are convoluting how ZeroMQ and CurveMQ work. ZMQ simply abstracts how clients talk over a network. Pub-Sub is a fine example of that since you, as a developer can write programs where clients can fan-out messages, i.e. from one node to many others in one direction.
This does not mean, however, that this is what actually happens. In fact, ZMQ opens as many (bidirectional) TCP connections between the publisher and all the subscribers and sends pretty much the same message from the publisher to all the subscribers, each in its own connection.

What this means for encryption is that the high-level message you send is actually encrypted with the public key of each subscriber and then sent individually. In fact, a single subscriber could never decrypt a message that was sent to another subscriber.

TL;DR it just _seems_ as though the publisher is "encrypting" the message once with his private key, but in fact the message is encrypted as many times as there are subscribers.

Cheers!
alex.


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Disclaimer:

If you are not the intended recipient of this email, please notify the sender and
delete it.
Any unauthorized copying, disclosure or distribution of this email or its
attachment(s) is forbidden.
Thales Nederland BV will not accept liability for any damage caused by this email or
its attachment(s).
Thales Nederland BV is seated in Hengelo and is registered at the Chamber of
Commerce under number 06061578.
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[Holger Joukl]

Hi,

(silent lurker on this list and no curve experience at all, but...)

Post by LENFERINK Roy
I would like to swap the keys, so, the publisher should encrypt the data
with his public key, and the subscribers should decrypt the data using
the private key of the publisher.

There seems to be some serious misunderstanding here imho:
Never ever give the private key (yours, or the publisher's) to someone else
(anybody, or the subscribers).

Holger

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