Encryption & Range

[Renamon]

Is there a significant, real-world reduction in range using encrypted P-25 over clear P-25? If so, do different algorithms have different (real world) ranges?

I'm just curious why more entities do not use encryption. I have read that cost, key management and/or interoperability are reasons they do not.

What do you think?

[com501]

Digital is digital.

There is no range difference in P25 or Trbo when encrypted.

Most departments don't use encryption because a) it s a hassle and b) its not needed.

Although with the $10 ADP option, encryption for P25 is a lot more affordable.

[RFguy]

Digital is digital.

There is no range difference in P25 or Trbo when encrypted.

This is true for basic privacy on MOTOTRBO, but not enhanced privacy. Enhanced privacy does increase system access time and does cause some degradation of audio quality.

Here's a quote from the system planner:

Enhanced Privacy uses multiple keys and a random number to ensure that the encryption data is different for each data message and each superframe of a voice message. This requires transporting crypto parameters (e.g. key Identifier, Initialization Vector) with the voice or data payload. A voice message, in the case of Enhanced Privacy, requires an additional header and replaces some of the least important bits of the voice payload with the Initialization Vector. The additional header increases the System Access Time except when Talk Permit Tone is enabled (in repeater mode) where the additional header replaces one of the normal voice headers. The replacement of payload bits reduces the voice quality. Note that the reduction in voice quality is barely noticeable.

[RRSM]

There is a pretty noticable degradation in voice quality I have noticed when enhanced privacy is used, as opposed to basic or none.

[MattSR]

Its not an inherent problem with encrypted digital voice - P25 theres no difference in range or quality.

The reason TRBO loses quality is because of the way Motorola chose to implement it - not because encryption somehow automatically degrades the quality.

[com501]

Digital is digital.

There is no range difference in P25 or Trbo when encrypted.

This is true for basic privacy on MOTOTRBO, but not enhanced privacy. Enhanced privacy does increase system access time and does cause some degradation of audio quality.

Here's a quote from the system planner:

Enhanced Privacy uses multiple keys and a random number to ensure that the encryption data is different for each data message and each superframe of a voice message. This requires transporting crypto parameters (e.g. key Identifier, Initialization Vector) with the voice or data payload. A voice message, in the case of Enhanced Privacy, requires an additional header and replaces some of the least important bits of the voice payload with the Initialization Vector. The additional header increases the System Access Time except when Talk Permit Tone is enabled (in repeater mode) where the additional header replaces one of the normal voice headers. The replacement of payload bits reduces the voice quality. Note that the reduction in voice quality is barely noticeable.

Um, 'system access time' DOES NOT EQUAL 'range difference'.

[wavetar]

Um, 'system access time' DOES NOT EQUAL 'range difference'.

I believe he's referring to this line:

A voice message, in the case of Enhanced Privacy, requires an additional header and replaces some of the least important bits of the voice payload with the Initialization Vector...The replacement of payload bits reduces the voice quality. Note that the reduction in voice quality is barely noticeable.

It stands to reason that any reduction in DAQ would equal a corresponding reduction in usable range, whether it's a linear relationship or not.