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,
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
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!
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| caller' SAS must match callee's |
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| Prefix | figure |
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| SubtitleText | caller' SAS |
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The caller reads his key out loud (
) and the callee can check they match his owns ().Verify call security on iPhone: matching key exchanges, so the call is secure!
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| must match callee's one | | AnchorName | iphone_sas |
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| | Image Modified |
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The caller reads his key out loud (
) and the callee can check they match his owns ().Verify call security on Android: matching key exchanges, so the call is secure!
| Subtitle |
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| Prefix | figure |
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| SubtitleText | The caller reads his key out loud |
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| AnchorName | android sas 1 |
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Image Removed |
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| caller' SAS must match callee's one | | AnchorName | android_sas |
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The caller Caller reads his key out loud (
) and the callee can check loud and callee checks they match his owns
().
| Note |
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| 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
| Subtitle |
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| Prefix | figure |
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| SubtitleText | Trusted contacts |
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| AnchorName | bb_trusted_contacts |
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| Image Added |
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| Prefix | figure |
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| SubtitleText | Trusted contacts |
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| AnchorName | iphone_trusted_contacts |
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| | Image Added |
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| Prefix | figure |
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| SubtitleText | Trusted contacts |
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| AnchorName | android_trusted_contacts |
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| | Image Modified |
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| Warning |
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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. |
Identifying a wiretapping attempt
Attempt to wiretap a call to a "trusted" contact
If a third party attempts to wiretap a call to a contact previously "trusted" by you
automatically detects the wiretapping attempt, interrupts the call and displays the following security alert.
...
After receiving a security alert, you must always verbally re-verify the SAS after the cryptographic key exchange and re-trust your contact for future calls (see chapter Verifying call security).
In the event of a third party attempts to wiretap a call when you're speaking to a contact not yet saved as trusted,
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!
| Subtitle |
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| Prefix | figure |
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| SubtitleText | SAS on the caller's phone |
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| AnchorName | wiretap 1 |
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| Image Removed |
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| Prefix | figure |
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| SubtitleText | SAS on the calle's phone don't match |
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| AnchorName | wiretap2 |
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| Image Removed |