What are IS-54 and IS-136: TDMA?

IS-54 and IS-136 are standards for TDMA American Digital Cellular.

Mobile Frequency Range	Rx: 869-894; Tx: 824-849
Multiple Access Method	TDMA/FDM
Duplex Method	FDD
Number of Channels	832 (3 users per channel)
Channel Spacing	30Khz
Modulation	DQPSK
Channel Bit Rate	48.6Kb

IS-54 and IS-136: TDMA Security

IS-54 and IS-136 use the CAVE (Cellular Authentication, Voice Privacy and Encryption) algorithm for authentication and the CMEA (Cellular Message Encryption Algorithm) for encryption.

CAVE and CMEA are documented in Common Cryptographic Algorithms and Interface Specification for Common Cryptographic Algorithms.

David Wagner, Bruce Schneier and John Kelsey published Cryptanalysis of the Cellular Message Encryption Algorithm, which documents deep flaws in the CMEA algorithm.