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This article presents a novel cryptosystem for secure transmission of color images through a coordinate cryptosystem as well as a geometric cryptosystem with time domain and frequency domain. In this technique, we have designed image encryption and decryption by a proposed random matrix shift cipher (RMSC) associated with a discrete fractional Fourier transform (DFrFT). Our proposed random matrix shift cipher is a coordinate and geometric cryptosystem for security of color image data which is completely different from existing cryptosystems for security of any data. The combination of a random matrix shift cipher and discrete fractional Fourier transform provide a robust cryptosystem for color image data in the time domain as well as the frequency domain without loss of any information. Existing techniques provide single-layer protection of color image data, but the cryptosystem presented here gives multiple layers of protection. Computer simulation on a standard example (Lena and Barbara color im...

This article presents Christian ciphers counterparts of the well-known Hebrew atbah cipher used in main languages and scripts of the Christan Orient: in Greek, Coptic, and Syriac, in Late Antiquity and the Middle Ages. The article also describes other alphabetic substitution ciphers used in these languages and highlights numerical rules in their construction.

This article is an exposition of a pencil and paper cipher used by Soviet secret agents working inside the U. S. that successfully defied the government's computer-aided attempt at cryptanalysis for several years.

An early Indian cipher that dates perhaps as early as 4th century A.D. is described. Basically, this cipher maps numerals into consonants; the vowels between the consonants may be used freely.

In 1915 First Lt. Joseph O. Maubourgne, later MG Maugorne and Chief Signal Officer, 1937–1941, presents a simple substitution cipher challenge to the Army Signal School. He proposes a test to determine if his new cryptosystem should replace the Cipher Disk and Playfair Cipher then in use.