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Crypto phones
Secure telephone equipment

Secure telephones are telephones that provide some level of voice security, in order to protect the calling parties from eavesdropping. Crypto phones are a special type of secure telephones that use advanced digital techniques for the encryption of voice data. Depending on the type and level of encryption used, crypto phones may be restricted or classified items.

Computer algorithms for government and military use, are generally controlled by the National Security Agency (NSA) in the US. They are divided into several security levels, of which Type 1 represents the highest level of security. Such devices can safely be used for top secret messages.

Secure telephones on this website
SIGSALY secure telephony system (Ciphony I) British WWII scrambler phone KY-3 wideband secure voice system with KYX-9 desk set Secure Telehone Unit STU-I (KY-70) Secure Telehone Unit (ITT, Northern Telecom) Motorola STU-II/B SECTEL (NATO-version) Secure Telehone Unit (Motorola, AT&T, RCA, etc.) Secure Terminal Equipment
Motorola SECTEL range of secure telephones AT&T/Lucent 1100 STU-III secure phone (later sold by General Dynamics) CVAS III Secure Telephone KY-68 Digital Secure Telephone Philips Spendex-40 secure telephone for voice, fax and computer Philips Spendex-50, military secure crypto phone (a.k.a. DBT) Philips PNVX secure crypto telephone Racal MA-44741 Secure Phone Adapter
Simple digitially controlled analogue voice scrambler AT&T TSD-3600 Telephone Encryptor AT&T/Lucent 4100 crypto phone (later sold by General Dynamics) The Siemens DSM Voice telephone encryptor Siemens Crypset 100 crypto phone Hagelin (Crypto AG) HC-3300 crypto phone Hagelin HC-4220 Fax Encryptor Hagelin HC-2203 PSTN Phone Encryptor
Mieco 25A telephone scrambler Telsy TDS-2003 portable voice encryptor Telsy TDS-2004 telephone voice encryptor Telsy Cryptophone 7000 Terma ET-10, Digital Tactical Terminal with secure voice and data capability Siemens CTE-020 Remote Digital Engineering Order-Wire Terminal Tele Security Timmann, TST-7700 Voice and data encryption system Gretacoder 101, speech scrambler
Mobile frequency and time domain voice scrambler Elcrovox 1-4D narrow band voice and data terminal (STU-II compatible) Rohde & Schwarz Elcrodat 6-2 Not truely a crypto phone, but usable on crypto-enabled telephone exchanges
Secure GSM phone
Voice scramblers
Older types of secure telephones generally use a technique called frequency inversion. They are sometimes called scramblers and are inherently insecure. An example of such a scrambler phone is the Mieco 25A (shown above). Even voice scramblers that use time-division speech scrambling should be considered insecure by today's standards, even when the two techniques are combined.

 More about scramblers

Further information
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Crypto Museum. Created: Wednesday 07 December 2011. Last changed: Tuesday, 20 March 2018 - 17:48 CET.
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