Crypto phone
Encyclopedia
Crypto phones are mobile telephones that provide security against eavesdropping and electronic surveillance.
The interception of telecommunications has become a major industry. Most of the world's intelligence agencies and many private organisations intercept telephone communications
to obtain military, economic and political information. The price of simple mobile phone surveillance
devices has become so low that many individuals can afford to use them.
Advances in technology have made it difficult to determine who is intercepting and recording private communications.
Crypto phones can protect calls from interception by using algorithms
to encrypt the signals. The phones have a cryptographic chip
that handles encryption
and decryption. Two algorithms are programmed into the chip: A key-exchange algorithm for the key agreement protocol and a symmetric-key algorithm
for voice encryption.
by the cryptographic chip. When the IMSI-catcher
performs a man-in-the-middle attack
and disables the GSM encryption, the crypto phone encryption remains intact. Therefore, while the signal is still being intercepted, it can no longer be decoded and fake SMS
messages can't be sent as the IMSI-catcher does not have the correct code.
by using the hash function
. Then the session key becomes a confirm code. The confirm code could be 3 letters or 4 numbers, depending on the phone's manufacturer. In the crypto mode, the user reads the confirm code over the encrypted line to his communication partner and verifies the confirm code his partner reads back. If there is a discrepancy in the confirm code, a man-in-the-middle attack has been detected.
method.
The interception of telecommunications has become a major industry. Most of the world's intelligence agencies and many private organisations intercept telephone communications
Lawful interception
Lawful interception is obtaining communications network data pursuant to lawful authority for the purpose of analysis or evidence. Such data generally consist of signalling or network management information or, in fewer instances, the content of the communications...
to obtain military, economic and political information. The price of simple mobile phone surveillance
Phone surveillance
Phone surveillance is the act of performing surveillance of phone conversations, location tracking and data monitoring of a phone. Before the era of mobile phones, these used to refer to the tapping of phone lines via a method called wiretapping...
devices has become so low that many individuals can afford to use them.
Advances in technology have made it difficult to determine who is intercepting and recording private communications.
Crypto phones can protect calls from interception by using algorithms
Cryptographic primitive
Cryptographic primitives are well-established, low-level cryptographic algorithms that are frequently used to build computer security systems. These routines include, but are not limited to, one-way hash functions and encryption functions.- Rationale :...
to encrypt the signals. The phones have a cryptographic chip
Secure cryptoprocessor
A secure cryptoprocessor is a dedicated computer on a chip or microprocessor for carrying out cryptographic operations, embedded in a packaging with multiple physical security measures, which give it a degree of tamper resistance....
that handles encryption
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
and decryption. Two algorithms are programmed into the chip: A key-exchange algorithm for the key agreement protocol and a symmetric-key algorithm
Symmetric-key algorithm
Symmetric-key algorithms are a class of algorithms for cryptography that use trivially related, often identical, cryptographic keys for both encryption of plaintext and decryption of ciphertext. The encryption key is trivially related to the decryption key, in that they may be identical or there is...
for voice encryption.
Prevention
For the system to work, both users must have crypto phones logged into crypto mode. As with other phones, the signal is encripted by GSM but it is also encryptedSuperencryption
Multiple encryption is the process of encrypting an already encrypted message one or more times, either using the same or a different algorithm. The terms cascade encryption, cascade ciphering, multiple encryption, multiple ciphering, and superencipherment are used with the same meaning...
by the cryptographic chip. When the IMSI-catcher
IMSI-catcher
An IMSI catcher is an eavesdropping device used for interception of cellular phones and usually is undetectable for users of mobile phones. Such a virtual base transceiver station is a device for identifying the International Mobile Subscriber Identity of a nearby GSM mobile phone and...
performs a man-in-the-middle attack
Man-in-the-middle attack
In cryptography, the man-in-the-middle attack , bucket-brigade attack, or sometimes Janus attack, is a form of active eavesdropping in which the attacker makes independent connections with the victims and relays messages between them, making them believe that they are talking directly to each other...
and disables the GSM encryption, the crypto phone encryption remains intact. Therefore, while the signal is still being intercepted, it can no longer be decoded and fake SMS
SMS
SMS is a form of text messaging communication on phones and mobile phones. The terms SMS or sms may also refer to:- Computer hardware :...
messages can't be sent as the IMSI-catcher does not have the correct code.
Authentication
At the beginning of the call, both users get the same session keySession key
A session key is a single-use symmetric key used for encrypting all messages in one communication session. A closely related term is traffic encryption key or TEK, which refers to any key used to encrypt messages, as opposed to other uses, like encrypting other keys .Session keys can introduce...
by using the hash function
Hash function
A hash function is any algorithm or subroutine that maps large data sets to smaller data sets, called keys. For example, a single integer can serve as an index to an array...
. Then the session key becomes a confirm code. The confirm code could be 3 letters or 4 numbers, depending on the phone's manufacturer. In the crypto mode, the user reads the confirm code over the encrypted line to his communication partner and verifies the confirm code his partner reads back. If there is a discrepancy in the confirm code, a man-in-the-middle attack has been detected.
Key Erase
The "session code" that has been established is used only for that specific call. At termination, all the parameters are wiped from memory, and there is no way to reconstruct the code. Intercepted and stored encrypted material can be kept for later analysis, but there is no way to break the code except, possibly, by the time consuming trial-and-errorTrial and error
Trial and error, or trial by error, is a general method of problem solving, fixing things, or for obtaining knowledge."Learning doesn't happen from failure itself but rather from analyzing the failure, making a change, and then trying again."...
method.