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CHAPTER 5 Cryptography > Modern cryptographic tools - Pg. 69

Cryptography CHAPTER 5 4 The system ought to be compatible with telegraph communication. 5 The system must be portable, and its use must not require more than one person. 6 Finally, regarding the circumstances in which such system is applied, it must be easy to use and must require neither the stress of mind nor the knowledge of a long series of rules. Although several of these principles have become outmoded with the advent of computers to aid in cryptography, the second principle has become a tenet of cryptographic algorithms. This idea was later restated by Claude Shannon as "the enemy knows the system" [4]. Both versions of this concept mean that cryptographic algorithms should be robust enough that, even though someone may know every bit of the system with the exception of the key itself, he or she should still not be able to break the encryption. This idea represents the opposite approach to "security through obscurity" and is one of the underlying principles for many modern cryptographic systems. 69 MODERN CRyPTOgRAPHIC TOOLS Although very efficient electromechanical cryptographic systems existed, such