The "Top Secret" level applies an End-To-End security model, with audio model encrypts audio data encrypted on one end point of the call and decrypted it decrypts audio stream on the other end point one without any possibility to intercept it in the middle. middle point exchange. When using End-to-End Security model,

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relies on ZRTP protocol so there is no need to deploy a any PKI infrastructure, but a it's required human verification is required on each call, so to exclude the presence of a possible MITM (Man In The Middle) attacker.

Verifying call security

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Professional uses an encryption and security system based on ZRTP protocol. This protocol is based on " human " verification of two words (called Short Authentication String or SAS) displayed at the beginning of a call. The SAS are made up of two words in English, randomly generated for each call. The same SAS displayed on the two phones must be verbally compared by the two callers to guarantee call security. After the security was verified the two peers could trust each other.

Verify call security

...

: matching

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keys means the call is secure!

 

 

The caller reads his key out loud (

Xref
AnchorName bb sas 1

) and the callee can check they match his owns (

Xref
AnchorName bb sas 2

).

Verify call security on iPhone:  matching key exchanges, so the call is secure!

 

 

The caller reads his key out loud (

Xref
AnchorName iphone sas 1

) and the callee can check they match his owns (

Xref
AnchorName iphone sas 2

).

Verify call security on Android:  matching key exchanges, so the call is secure!

 

The caller Caller reads his key out loud (

Xref
AnchorName android sas 1

) and the callee can check loud and callee checks they match his owns (

Xref
AnchorName android sas 2

).

 

Note
title Suggestion
After making sure the Short Authentication Strings match and that the called party is really the person you are speaking to, save the contact in the phone book as "trusted" by clicking Trust. This way you need not verify the key exchange next time you call this (trusted) contact in the future.The Short Authentication Strings will no longer be highlighted in orange. Security is guaranteed by the ZRTP key continuity feature.

In normal conditions subsequent communications with a "trusted" contact can start without the need of verbal verification. Short Authentication Strings background color will be different and SAS should only be verified in the event of wiretapping attempts or change to one of the two phones' configurations. In this case, the keys must be verbally verified or the call immediately interrupted.

Secure call between trusted contacts

 

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Warning
title Warning
If the SAS does not match with your peer's one you should immediately hang up the call as this might be a sign of a Man in the Middle interception attack.

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In the event of a third party attempts to wiretap a call when you're speaking to a contact not yet saved as trusted,

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displays two displays different Short Authentication String on the two phones. The callers caller should verbally verify the differences between the two key exchanges and interrupt the call.

NON matching key exchanges: wiretapping attempt in progress!

 

 

 

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