Terry Ritter

Analyst. Designer. Consultant.
Cryptography. Software. Analog. Digital.

2609 Choctaw Trail
Austin, Texas 78745-1511

E-mail Preferred: ritter@ciphersbyritter.com

Phone / Answer Machine: 512-892-0494




  • An independent professional since 1981


  • Author of technical articles
  • Analyst of scientific argument
  • Consultant in cryptography, cipher systems, software, computation and electronics
  • Inventor of fundamental cryptographic technology
  • Supplier of patented technology
  • Designer of custom ciphers and electronic systems
  • Programmer of embedded systems
  • Systems Analyst of cryptographic, digital and software systems
  • Academic Article Referee for various journals



  • Owner, Ritter Software Engineering, 1991-2005
  • Licensed Professional Electrical Engineer, 1980-2005
  • Senior Member of IEEE, 1974-2005
  • Member of ACM, 1975-2005
  • Cryptography Consultant to Bankers Trust
  • Owner, Blue Jean Software
  • Article Referee for Cryptologia
  • Professional Witness by deposition
  • Software Designer of dedicated multiprocessor LAN, 1982
    • Both closely-coupled and loosely-coupled real-time multiprocessing.
    • Fiber-optic main high-speed communications.
    • Full dynamic flow-control with error-check and retry.
  • Adjunct Assistant Professor of Electrical Engineering at Georgia Tech, Aug.-Dec. 1980
    • Wrote half the course and delivered half the lectures on developing software for microprocessor-based equipment designs.
    • Based the labs on early versions of BASIC09 and OS9.
  • Staff Engineer, Motorola MOS Division, Microcomputer Systems Design Group, Jul. 1976 - Jan. 1981. Architect of Microcomponent Chips, including 6809 Advanced Microprocessor specification, architecture and assembly language. Architect of structured BASIC language for 6809.
    • Software Engineer, 1979-81
    • Originator, Principal Systems Engineer and "Keeper of the Specification" -- MC6809 Advanced Microprocessor, 1977-80 [I have some Motorola MC68B09EP's made in the 20th week of 1999, thus marking almost 20 years of 6809 production!]
    • Project Engineer -- MC6809 Breadboard, 1978-79
      The LS-TTL "breadboard" of the MC6809 NMOS design.
    • Originator and Supervising Project Engineer -- BASIC09, 1978-80
      A structured BASIC language project, with operating system OS9 and associated specifications.
    • Systems Engineer. One of several engineers on MC6802, MC6845 CRTC, and MC6847 VDG, and other designs.
  • Fixed Ciphony Repair Specialist (32F20) in U.S. Army, Nha Trang Sig Bn (AUTODIN ASC), South Vietnam, 1967-68.

INVENTOR of fundamental cryptographic technology:

  • U.S. Patent 4,979,832. Dec. 25, 1990. Ritter, Terry F. DYNAMIC SUBSTITUTION COMBINER AND EXTRACTOR. A "cryptographic combiner," for invertibly yet nonlinearly mixing a stream-cipher keying sequence with data. Conceptually, a keyed exclusive-OR with strength.
  • U.S. Patent 5,623,549. Apr. 22, 1997. Ritter, Terry F. CIPHER MECHANISMS WITH FENCING AND BALANCED BLOCK MIXING. A structure for invertibly mixing two input blocks into two resulting blocks in a statistically-balanced way. This is one way to build a large block cipher from relatively small S-boxes. Of multiple implementations, some are keyed and nonlinear.
  • U.S. Patent 5,727,062. Mar. 10, 1998. Ritter, Terry F. VARIABLE SIZE BLOCK CIPHERS. A structure for building block ciphers with dynamically-variable block size. When coupled with random-length header and trailer fields, VSBC's provide a new level of block cipher strength by not giving the opponent even a block to work on.

AUTHOR of archived web articles:

AUTHOR of articles with JavaScript functioning tools:

AUTHOR of journal articles:

  • Ritter, T. 1999. "Cryptography: Is Staying with the Herd Really Best?." IEEE Computer. August. 32(8): 94-95.
  • Ritter, T. 1994. "Estimating Population from Repetitions in Accumulated Random Samples." Cryptologia. 18(2):155-190.
  • Ritter, T. 1991. "Voice and Video Cryptography in a DSP Environment." Presented at, and published in, The Proceedings of The Second Annual Texas Instruments TMS320 Educators Conference, August 5-7 1992, in Houston, Texas.
  • Ritter, T. 1991. "The Politics of Software Patents." Midnight Engineering. May-June: 29-35.
  • Ritter, T. 1991. "The Efficient Generation of Cryptographic Confusion Sequences." Cryptologia. 15(2): 81-139.
  • Ritter, T. 1991. "Transposition Cipher with Pseudo-Random Shuffling: The Dynamic Transposition Combiner." Cryptologia. 15(1):1-17.
  • Ritter, T. 1990. "Substitution Cipher with Pseudo-Random Shuffling: The Dynamic Substitution Combiner." Cryptologia. 14(4): 289-303
  • Ritter, T. 1986. "The Great CRC Mystery." Dr. Dobb's Journal of Software Tools. February. 11(2): 26-34, 76-83.
  • Ritter, T. 1980. "Modular and Structured Programming on Small Systems." Systems News (Motorola Semiconductor Products marketing magazine). October. 1(5): 10-13.
  • Ritter, T. and G. Walker. 1980. "Varieties of Threaded Code for Language Implementation." Byte. 5(9): 206-117. Described as: "the best article ever published on the subject" (Mike Coughlin, mikc@gnu.ai.mit.edu).
  • Ritter, T. 1980. "Modular and Structured Programming on Small Systems." The Best of the Computer Faires, Volume 5: Conference Proceedings of the 5th West Coast Computer Faire (March 14-16, 1980). (Jim C. Warren, Jr., Editor)
  • Ritter, T. 1979. "Standard Product ROM's (SPR's)." Proceedings of the IEEE Computer Society, MICRO Computer Firmware and I/O Workshops (presented April 10, 1979). 109-114.
  • Ritter, T. 1979. "Programming the 6809." 68 Micro Journal. 1(9): 34-37.
  • Ritter, T. 1979. "Upward Compatibility: More Power--Less Pain." The Best of the Computer Faires, Volume 4: Conference Proceedings of the 4th West Coast Computer Faire (May, 1979). 351-358.
  • Ritter, T. 1979. "M6809 is Silicon." Byte. 4(5): 30-31.
  • Ritter, T. and J. Boney. 1979. "A Microprocessor for the Revolution: The 6809."
    • "Part 3: Final Thoughts." Byte. 4(3): 46-52
    • "Part 2: "Instruction Set Dead Ends, Old Trails, and Apologies." Byte. 4(2): 32-42.
    • "Part 1: Design Philosophy." Byte. 4(1): 14-42. Cover Article.
  • Ritter, T. 1978. "Resident Memory Test Systems, With an Example for the 6800" (sic). Dr. Dobb's Journal of Computer Calisthenics and Orthodontia. 3(5): 28-33.
  • Wiles, M., F. Musa, T. Ritter, J. Boney and T. Gunter. 1978. "Compatibility Cures Growing Pains of Microcomputer Family." Electronics. February 2, 1978. 95-103. Cover Article.
  • Ritter, T. 1976. "The Absolute Field in Direction Antennas." BM/E (Broadcast Management / Engineering). March. 46-52.
  • Ritter, T. 1975. "The Directional Antenna Pattern." BM/E (Broadcast Management / Engineering). April. 56-66.
  • Blakely, P. and T. Ritter. 1972. "A Talk Show Delay System." Broadcast Engineering. February. 42-45.

AUTHOR of archived literature surveys:

DESIGNER of ciphers:

  • Variable Size Block Ciphers (1995) -- A variety of new block cipher designs with dynamically-variable block size. These ciphers will avalanche the entire output block if even one bit of the input block changes, just as we expect from any conventional block cipher.
  • Fenced DES (1994) -- "A larger and better DES." A 256-bit block cipher which uses DES as a component. Stronger than DES, and faster than Triple-DES.
  • Fencing and Mixing Ciphers (1994) -- A variety of new block cipher designs using various forms of balanced mixing, as opposed to the usual Feistel "round-based" construction.

IMPLEMENTOR of software cryptosystems:

  • Cloak2 (1994) -- A highly-developed Dynamic Substitution file cipher product for DOS, with 992-bit secret keys.
  • Penknife (1993) -- A highly-developed Dynamic Substitution file cipher product for DOS, producing ASCII ciphertext for e-mail transmission




Terry Ritter, his current address, and his top page.

Last updated: 2005-10-14