Security Engineering, 3rd Edition

For my daughter, and other lawyers…

The tricks taught in this book are intended only to enable you to build better systems. They are not in any way given as a means of helping you to break into systems or do anything else illegal. So where possible I have tried to give case histories at a level of detail that illustrates the underlying principles without giving a ‘hacker's cookbook’.

Governments fought to restrict knowledge of cryptography until the turn of the century, and there may still be people who believe that the knowledge contained in this book should not be published.

Their fears were answered in the first book in English that discussed cryptology, a 1641 treatise on optical and acoustic telegraphy written by Oliver Cromwell's cryptographer and son-in-law John Wilkins [2025]. He traced scientific censorship back to the Egyptian priests who forbade the use of alphabetic writing on the grounds that it would spread literacy among the common people and thus foster dissent. As he said:

‘It will not follow that everything must be suppresst which may be abused… If all those useful inventions that are liable to abuse should therefore be concealed there is not any Art of Science which may be lawfully profest.’

The question was raised again in the nineteenth century, when some well-meaning people wanted to ban books on locksmithing. In 1853, a contemporary writer replied [1899]:

‘Many well-meaning persons suppose that the discussion respecting the means for baffling the supposed ...