Verify a Recipient Cryptographically in Signal Messenger
Signal Messenger allows anyone to verify a recipient using his/her unique cryptograpically generated safety number. This verification allows one to ensure no one is intercepting the message and also ensures the recipient is genuinely the right person.
Meet Up And Verify The Person Face-to-Face
To properly verify that individual, the recipient and you have to meet up once to verify each other physically for the first time.
You will need each other’s safety numbers QR codes for cryptographic verifications.
View Safety Number of Recipient
Once both of you are ready, simply select each others' recipient name at the title bar to enter the recipient profile.
When the profile appears, select the View Safety Number and let Signal present the cryptography key.
Both of you can then either:
- One of you press the QR code to scan the other one. Repeat this step for the other person; OR
- Verify the cryptography data manually.
If Signal does not throw any error and the verify button is not toggled to on, both of you can manually toggle it to on to indicate that the channel are verified.
At this point, both of you completed the verification process.
When Safety Number Has Changed
Whenever the safety number had changed, you should and shall re-verify the changes with your recipient again. The cause can be any of the following:
- There is a sim swap over a device (e.g. changing to new phone).
- The phone security is compromised.
- There is a possibility that the communication channel has interception.
Regardless of any of above, the point is that the channel has compromised so you should not communicate sensitive information until both of you rectified the issue and re-verified again.
For more information, please feel free to read the main support article here: https://support.signal.org/hc/en-us/articles/360007060632-What-is-a-safety-number-and-why-do-I-see-that-it-changed-
Epilogue
That’s all for “Verify a Recipient Cryptographically in Signal Messenger”. Should you have any question, please feel free to: