Substitution Cipher

What Does Substitution Cipher Mean?

A substitution cipher is a type of encryption where characters or units of text are replaced by others in order to encrypt a text sequence. Substitution ciphers are a part of early cryptography, predating the evolution of computers, and are now relatively obsolete.


Techopedia Explains Substitution Cipher

In a substitution cipher, a letter such as A or T, is transposed into some other letter, which effectively encrypts the sequence to a human reader. The issue is that simple substitution ciphers do not really encrypt effectively in terms of computer evaluation – with the rise of the personal computer, substitution ciphers became relatively easy for computers to crack. However, some of the ideas behind the substitution cipher continue to live on – some forms of modern encryption might use an extremely large text set and an extremely sophisticated substitution to effectively encrypt information.


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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…