PIN out of letters or symbols

[Marius_U]

I was pairing using nRF connect app via mobile phone and I noticed that there's a check mark which says "PIN contains letters or symbols":

Is there a pairing method which allows creating passkey containing letters and symbols? I always thought that there's four methods:

• Just works (would not apply to this case)
• Out of band (would not apply to this case)
• Passkey (always thought that it's always 6 numbers from 0 to 9)
• Numeric comparison (which by the name could be implied that we need to compare numbers)

Why this is an option?

[dejans]

Hi,

Are your devices able to pair in both cases - with and without checking "PIN contains letters or symbols" option?

Best regards,
Dejan

[Marius_U]

Yes, but I was wondering if there was a method to create passkey made out of letters and symbols, and since nRF connect app has such option maybe I was not aware of it. If so I would be interested in creating safer passkey.

[dejans]

Hi,

PassKey Entry is one of the four models supported by LE Secure Connections as shown in Bluetooth Pairing. The option "PIN contains letters or symbols" might provide a way to provide passkey mode out of letters and symbols. If it is checked, this option switches keyboard layout from showing digits (which is default) to qwerty, or at least suggests the switch of the current keyboard.

Best regards,
Dejan

[Marius_U]

So as I understand by your response it is possible to create passkey which contains letters and symbols. Can you give an example of how would that look like in zephyr?

[dejans]

Hi,

I had a discussion with the developers. Passkey is always 6 digits and Zephyr does not have support for this. The option in question might be related to Android system dialog and not nRF Connect app itself. Generally, there is 6-digit passkey which is random on every attempt. Security of fixed passkeys is roughly equivalent to Just Works. You should not consider this option as a new model separate from 4 existing models.

Best regards,
Dejan