conjugate coding
{{Use American English|date=January 2019}}
{{Short description|Quantum-based cryptographic method
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Conjugate coding is a cryptographic tool, introduced by Stephen Wiesner{{Cite journal|last=Wiesner|first=Stephen|date=1983|title=Conjugate Coding|journal=SIGACT News|volume=15|issue=1|pages=78–88|doi=10.1145/1008908.1008920|s2cid=207155055|issn=0163-5700}} in the late 1960s. It is part of the two applications Wiesner described for quantum coding, along with a method for creating fraud-proof banking notes. The application that the concept was based on was a method of transmitting multiple messages in such a way that reading one destroys the others. This is called quantum multiplexing and it uses photons polarized in conjugate bases as "qubits" to pass information.{{Cite book|title=Emerging Trends in ICT Security: Chapter 9. A Survey of Quantum Key Distribution (QKD) Technologies|last1=Morris|first1=Jeffrey|last2=Grimaila|first2=Michael|last3=Hodson|first3=Douglas|last4=Jacques|first4=David|last5=Baumgartner|first5=Gerald|publisher=Morgan Kaufmann Publishers|year=2013|isbn=9780128070666|location=San Francisco, CA}} Conjugate coding also is a simple extension of a random number generator.{{Cite book|title=Broadband Quantum Cryptography|last=Rogers|first=Daniel|publisher=Morgan & Claypool Publishers|year=2010|isbn=9781608450596|location=San Rafael, CA|pages=31}}
At the behest of Charles Bennett, Wiesner published the manuscript explaining the basic idea of conjugate coding with a number of examples but it was not embraced because it was significantly ahead of its time.{{Cite book|title=Quantum Bits and Quantum Secrets: How Quantum Physics is Revolutionizing Codes and Computers|last=Morsch|first=Oliver|publisher=John Wiley & Sons|year=2008|isbn=9783527407101|location=Berlin|pages=157}} Because its publication has been rejected, it was developed to the world of public-key cryptography in the 1980s as Oblivious Transfer, first by Michael Rabin and then by Shimon Even. It is used in the field of quantum computing. The initial concept of quantum cryptography developed by Bennett and Gilles Brassard was also based on this concept.