Here's a paper with the specific details of why P25 has troubles with reliability while encrypted: http://www.crypto.com/papers/p25sec.pdf http://www.crypto.co

Here's a paper with the specific details of why P25 has troubles with reliability while encrypted: http://www.crypto.com/papers/p25sec.pdf http://www.crypto.com/papers/p25sec.pdf "Because of the above-described property of the error correction mechanisms used, especially in voice frames such as the LDU1 and LDU2 frame types, there is no mechanism to detect errors in certain portions of transmitted frames. This was a deliberate design choice, to permit undetected corruption of portions of the frame that are less important for intelligibility."