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4. ISO/IEC JTC1, Information Technology, SC 27. 2nd ISO/IEC CD 13888-2 Information Technology — Security Techniques — Non-repudiation — Part2: Using symmetric encipherment algorithms. ISO/IEC JTC 1/SC 27 N 1106, July 1995.
5. ISO/IEC JTC1, Information Technology, SC 27. ISO/IEC CD 13888-3 Information Technology — Security Techniques — Non-repudiation — Part3: Using asymmetric techniques. ISO/IEC JTC 1/SC 27 N 1107, September 1995.