applied cryptography - protocols, algorithms, and source code in c

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Unformatted text preview: s for enumerating passphrases in order to exploit this. Until we have a better understanding of how to attack passphrases, we really have no idea how weak or strong they are. 6. Mismatched trust. Almost all currently available cryptographic software assumes that the user is in direct control over the systems on which it runs and has a secure path to it. For example, the interfaces to programs like PGP assume that their passphrase input always comes from the user over a secure path like the local console. This is not always the case, of course; consider the problem of reading your encrypted mail when logged in over a network connection. What the system designer assumes is trusted may not match the needs or expectations of the real users, especially when software can be controlled remotely over insecure networks. 7. Poorly understood protocol and service interactions. As systems get bigger and more complex, benign features frequently come back to haunt us, and it’s hard to know even where to look when things fail. The Internet worm was propagated via an obscure and innocent-looking feature in the sendmail program; how many more features in how many more programs have unexpected consequences just waiting to be discovered? 8. Unrealistic threat and risks assessment. Security experts tend to focus on the threats they know how to model and prevent. Unfortunately, attackers focus on what they know how to exploit, and the two are rarely exactly the same. Too many “secure” systems are designed without considering what the attacker is actually likely to do. 9. Interfaces that make security expensive and special. If security features are to be used, they must be convenient and transparent enough that people actually turn them on. It’s easy to design encryption mechanisms that come only at the expense of performance or ease of use, and even easier to design mechanisms that invite mistakes. Security should be harder to turn off than on; unfortunately, few systems actually work this way. 10. Little broad-based demand for security. This is a well-known problem among almost everyone who has tied his or her fortune to selling security products and services. Until there is widespread demand for transparent security, the tools and infrastructure needed to support it will be expensive and inaccessible to many applications. This is partly a problem of understanding and exposing the threats and risks in real applications and partly a problem of not designing syst...
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