opaque1
Simple command-line frontend for libopaque
Usage
Create new
OPAQUE
records
Create new
opaque
record
-
offline
Initiate new
online
registration
Respond to
new
online
registration
request
Finalize online
registration
Complete online
record
Server portion
of
online
registration
User portion
of
online
registration
Run OPAQUE
Server portion
of
OPAQUE
session
User portion
of
OPAQUE
session
Overview
The OPAQUE protocol is an asymmetric password-authenticated key-exchange. Essentially it allows a client to establish a shared secret with a server based on only having a password. The client doesn’t need to store any state. The protocol has two phases:
•
|
In the initialization phase a client registers with the server. |
|---|---|
•
|
In the AKE phase the client and server establish a shared secret. |
The initialization only needs to be executed once, the key-exchange can be executed as many times as necessary.
Initialization
Initializing OPAQUE (registration) can be done either online or offline. The online variant has the benefit that the server never learns anything about the users password, with the drawback that this requires 3 messages to be exchanged by the client and the server.
The offline initialization is much easier, however either the user learns the servers secret, or the server learns the users password. The latter might be useful if some organisation wants to enforce some password quality rules and check those upon registration. The drawback is that either way, some sensitive information leaks to the other party.
Offline Registration
-
echo -n password | ./opaque init user server >record 3>export_key
Online Registration
socat style
On the server:
-
socat tcp-l:23523,reuseaddr,fork system:"bash -c \'opaque server-reg user server 3>record\'"
On the client:
-
socat tcp:127.0.0.1:23523 exec:'bash -c \"opaque user-reg user server 3< <(echo -n password) 4>export_key\"'
tcpserver style
On the server:
-
s6-tcpserver 127.0.0.1 23523 bash -c 'opaque server-reg user server 3>record'
On the client:
-
s6-tcpclient 127.0.0.1 23523 bash -c "opaque user-reg user server <&6 >&7 3< <(echo -n password) 4>export_key"
Manually
It’s possible to do all 4 steps seperately, in case you cannot connect to the server directly, then:
The user initiates with:
-
echo -n password | opaque register >msg 3>ctx
The server gets msg and responds with rpub, while keeping rsec secret:
-
cat msg | opaque respond >rpub 3>rsec
The user receives rpub and creates stub record and optionally uses the export key to encrypt more data:
-
cat ctx | opaque finalize user server 4<rpub >record 3>export_key
the server finalizes the record by completing the stub record from the client:
-
cat rec | opaque store user server >record 3<rsec
Running OPAQUE
tcpserver style
On the server:
-
s6-tcpserver 127.0.0.1 23523 bash -c './opaque server user server context 3<record 4>shared_secret'
On the client:
-
s6-tcpclient 127.0.0.1 23523 bash -c "./opaque user user server context <&6 >&7 3< <(echo -n password) 4>export_key 5>shared_secret"
socat style
On the server:
-
socat tcp-l:23523,reuseaddr,fork system:"bash -c \'./opaque server user server context 3<record 4>shared_secret\'"
On the client:
-
socat tcp:127.0.0.1:23523 exec:'bash -c \"./opaque user user server context 3< <(echo -n password) 4>export_key 5>shared_secret\"'