Crypto Dictionary, book review: A useful A-Z of cryptography definitions

This slim, opinionated, technical and intermittently amusing volume is one to flip through and repeatedly return to.
Written by Mary Branscombe, Contributor

Crypto Dictionary: 500 Tasty Tidbits for the Curious Cryptographer • by Jean-Philippe Aumasson • No Starch/ Penguin Random House • 160 pages • ISBN: 9781718501409 • £20.99 / $24.99 

Cryptography might be the most important thing that you use every day -- from e-commerce to messaging apps to retrieving your email to getting money out of an ATM to satellite TV -- without knowing. It's a complex and important field that isn't usually amusing or accessible. 

Jean-Philippe Aumasson's Serious Cryptography is a classic (and serious) introduction to the field. Arranged as alphabetical dictionary definitions with occasional supplementary details, his Crypto Dictionary: 500 Tasty Tidbits for the Curious Cryptographer is a rather less serious, but surprisingly comprehensive, collection of nuggets of information about cryptography that will make you smile, and occasionally scratch your head. 

Sometimes the writing is pithy: Base64 is simply labelled "not encryption", while the fundamental cryptocurrency concept Proof of work is (accurately) defined as "cryptography's contribution to environmental problems". Sometimes it's both pithy and helpful: as well as calling blockchain "both a blessing and a curse", the book offers an even-handed discussion of the drawbacks and benefits of so much interest in the technology. 

Not all of the jokes are funny (or appropriate), with some being so cryptic that they will escape anyone who isn't an expert (although it's well worth researching why the author refers to Time AI as "the Fyre Festival of cryptography"). The author can't resist the odd hobbyhorse that doesn't contribute much, and you'll need some mathematical knowledge and a passing acquaintance with cryptography basics to get the most out of the more technical definitions.

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But there are also plenty of genuinely useful entries with helpful explanations, from the basics of Diffie-Hellman encryption to Bruce Schneier's famous warning signs for spotting cryptography systems that are more marketing hype than actual security. Crypto Dictionary covers standards, conferences, key websites, historical references and anecdotes -- like the infamous banking representative asking for the fundamental principles of TLS 1.3 to be changed when the standard was all but decided -- making it as much of a compendium as a dictionary. 

Crypto Dictionary won't teach you how to do cryptography or how to judge if something is cryptographically sound. But if you want to look up a specific cryptography cipher, technique or protocol, know what rainbow tables are and how they help crack passwords, or read about the difference between quantum and post-quantum cryptography (the former being both post-quantum but also not part of the latter), then this book is an ideal starting point. It will also probably pique your interest in some other concept as you turn to the relevant page.


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