Be aware before putting 4000 USD of your money to a device that is phony (in this case: GSMK CryptoPhone 500). My professional assessment is that the dishonesty, deception is reason enough to stop and ask serious questions here. Paying more expensive price don't make you more safe, the more so while having 2 units for 8000 USD, with no guarantees in case of theft, damage or loss. The voice protection may work well for your needs. Still, have a look below for the case study that without a shadow of a doubt puts in front of you my honest and unbiased professional assessment of an inapt design.

If you are a government official, a business person or someone required to have a secure phone line, you better question your options and make a well informed decision.

If you need a short range device inside of a building, a Decibit Crypto Phone is just right for you. Worldwide calls are made through any TCP/UDP internet connection as a gateway, not necessarily needing a phone operator's cell infrastructure.

1) This does not ENCRYPT any voice:

2) Wrong terminology:

3) Wrong concept:

4) Update:

This is NOT a CryptoPhone.

It's just a scrambling phone.
Like any other so called "encrypted" walkie-talkie,
which only do scramble.

Voice Data itself was never processed through an encryption algorithm to get encrypted.

There is only one TRUE voice ENCRYPTING mobile phone:



In depth analysis:

Analog to digital converted (ADC) microphone input, your voice, is sampled at 6667 Hz.
Digital to analog converted (DAC) headphone output is also using the same rate.
Both mobile phone's codec chip do both operations simultaneously since the voice call is full dublex and in real-time.

The encryption and wireless transfer processes operate on 64 byte blocks. This makes 104 blocks each second or 1 block every 9.6 ms per phone.
Every 9.6 ms one 64 byte block is transmitted from phone A to phone B. This is sampled microphone voice data from phone A.
With a 50% offset, that is 4.8ms, a block is transmitted from phone B to phone A. This is phone B's sampled microphone voice data.
During these time frames, both phones triple DES and AES-128 encrypt or decrypt the wireless transmitted blocks.

It is in fact pretty complex to manage all these operations at this relative high voice sampling and processing rate in same time.
This is achieved by implementing a complex interwoven processing scheme.

ADC samples are collected in a buffer byte by byte in 64 steps, according to sample rate. This timing must be respected otherwise there would be no flawless voice conversation possible.
At start, there is no voice data, so the headphones are silent. After 4 of those 64 byte blocks of delay, which is 38.4 ms, each side starts hearing the very first voice.
After these 4 cycles, the buffers are filled with valid voice data at both phones. Every following 64 byte sampling cycle has the same dynamics repeating until the end of the call.

In a 64 byte cycle, after having sampled the 1st byte, 5 of 64 microphone sample bytes from previous cycle that were saved in a buffer are sent to smart card chip.
The same happens for the next 12 sampling steps. A total of 13 new microphone ADC samples (1..13) were added to buffer while, 64 bytes previous ADC samples were sent to smart card chip for encryption.
While MCU is busy adding samples 14 to 16 to buffer, the smart card, which operates in parallel, already encrypted the message which is now ready to be read out.
In same time MCU reads out an encrypted message received from the other phone from the wireless chip, which also operates independently in parallel.
During sampling of bytes 17..32, in every of these 16 steps, 4 bytes result of encrypted message from the smart card chip is read back by the MCU.
During sampling of bytes 30..45, in every 13 steps, 5 bytes of the received encrypted message from other phone is sent to the smart card chip for decryption.
During the next 3 sampling time from 46..48, the wireless chip is given the encrypted message that was read out from smart card chip while sampling period of 17..32 to be sent out to other phone.
In the last 16 sampling block of 49..64, the by now decrypted message from other phone is read out in steps of 4 bytes, which at the end of the cycle is added to the DAC buffer.

The workings between the codec chip, the micro controller unit, the wireless chip and the smart card chip are indeed complex, timed, interwoven and parallelized.
Codec chip gets DAC from MCU (from other phone) and sends ADC to MCU (from this phone).
Smart card chip is given plain data by MCU, after encryption using triple DES, being read out the encrypted data by MCU to be sent out to other phone.
Smart card chip is given encrypted data, that was encrypted by the other phone's smart card chip, after decrypted, being read out as plain data.
Wireless chip sends and receives encrypted 64 byte blocks.

Wireless chip further encrypts and decrypts on it's own 64 bytes in AES-128 to protect and to have encrypted wireless transmission.
The smart card chip encrypts and decrypts 64 byte blocks in triple DES.
Wireless chip's AES-128 encryption is performed on top of the smart cards triple des encrypted 64 byte data blocks.
Codec voice data is thus double layer encrypted.

Two different session keys, each 16 bytes for AES-128 and triple DES, are generated within the smart card chip for every call
using it's true random number generator and then exchanged between smart card chips using 2048 bits RSA.

For further product details, please visit: Decibit Crypto Phone