OTR
Version 9 (Adrian Georgescu, 09/13/2013 02:08 am)
| 1 | 3 | Adrian Georgescu | h1. Blink OTR implementation |
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| 2 | 1 | Adrian Georgescu | |
| 3 | 6 | Adrian Georgescu | "Blink SIP client for SIP2SIP edition":http://download.sip2sip.info/ is a multimedia SIP client that supports chat sessions using MSRP protocol (RFC4975 http://tools.ietf.org/html/rfc4975). The client is designed to work with SIP2SIP service that implements MSRP relay protocol for NAT traversal of SIP sessions with MSRP media like Instant Messaging chat sessions. |
| 4 | 2 | Adrian Georgescu | |
| 5 | 7 | Adrian Georgescu | Over the MSRP media chat session, Blink implements the OTR protocol. |
| 6 | 1 | Adrian Georgescu | |
| 7 | 3 | Adrian Georgescu | h2. OTR Protocol |
| 8 | 3 | Adrian Georgescu | |
| 9 | 9 | Adrian Georgescu | "Off-the-Record (OTR) Messaging":http://www.cypherpunks.ca/otr/ allows two parties to have private conversations over instant messaging by providing: |
| 10 | 3 | Adrian Georgescu | |
| 11 | 1 | Adrian Georgescu | h3. Encryption |
| 12 | 1 | Adrian Georgescu | |
| 13 | 1 | Adrian Georgescu | No one else can read your instant messages. |
| 14 | 1 | Adrian Georgescu | |
| 15 | 1 | Adrian Georgescu | h3. Authentication |
| 16 | 3 | Adrian Georgescu | |
| 17 | 1 | Adrian Georgescu | You are assured the correspondent is who you think it is. |
| 18 | 1 | Adrian Georgescu | |
| 19 | 1 | Adrian Georgescu | h3. Deniability |
| 20 | 1 | Adrian Georgescu | |
| 21 | 1 | Adrian Georgescu | The messages you send do not have digital signatures that are checkable by a third party. Anyone can forge messages after a conversation to make them look like they came from you. However, during a conversation, your correspondent is assured the messages he sees are authentic and unmodified. |
| 22 | 1 | Adrian Georgescu | |
| 23 | 1 | Adrian Georgescu | h3. Perfect forward secrecy |
| 24 | 1 | Adrian Georgescu | |
| 25 | 1 | Adrian Georgescu | If you lose control of your private keys, no previous conversation is compromised. |
| 26 | 3 | Adrian Georgescu | |
| 27 | 3 | Adrian Georgescu | h2. Implementation |
| 28 | 1 | Adrian Georgescu | |
| 29 | 8 | Adrian Georgescu | The OTR implementation is backwards compatible with MSRP clients that do not support it (of course the encryption feature are not available in this case). OTR is not employed on the remote party is a multi-party conference server (advertised by is-focus Contact header parameter). |
| 30 | 7 | Adrian Georgescu | |
| 31 | 4 | Adrian Georgescu | h3. User input |
| 32 | 4 | Adrian Georgescu | |
| 33 | 1 | Adrian Georgescu | * Chat window has the Encryption toolbar icon, encryption features for each session can be controlled by clicking on this toolbar item, a contextual menu appears |
| 34 | 4 | Adrian Georgescu | * Verification of remote identity can be performed using SMP protocol |
| 35 | 7 | Adrian Georgescu | * Each Contact can have encrypted related attributes saved (always use OTR, verification status and learned fingerprint) |
| 36 | 1 | Adrian Georgescu | |
| 37 | 4 | Adrian Georgescu | h3. Notifications |
| 38 | 4 | Adrian Georgescu | |
| 39 | 7 | Adrian Georgescu | When the remote party (identified by its SIP URI) has changed its encryption fingerprint, several visual and audible clues appear: |
| 40 | 4 | Adrian Georgescu | |
| 41 | 4 | Adrian Georgescu | * Chat window system message is displayed |
| 42 | 4 | Adrian Georgescu | * Voice synthesiser speaks |
| 43 | 1 | Adrian Georgescu | * System notification (OSX >=10.8) |
| 44 | 1 | Adrian Georgescu | * Growl notification |
| 45 | 8 | Adrian Georgescu | |
| 46 | 8 | Adrian Georgescu | |
| 47 | 8 | Adrian Georgescu | h3. Interoperability |
| 48 | 8 | Adrian Georgescu | |
| 49 | 8 | Adrian Georgescu | We are not aware of any other SIP/MSRP client implementation that supports OTR encryption today. Blink however interoperates well with XMPP clients when using SIP2SIP service built-in SIP/XMPP gateway. We were able to have bidirectional OTR encrypted chat sessions between Blink (using sIP/MSRP) and Jitsi (using XMPP). |