计算机类外文文献翻译---java核心技术

计算机类外文文献翻译---java核心技术内容摘要：

tion, you saw how to pute a message digest, a fingerprint for the original message. If the message is altered, then the fingerprint of the altered message will not match the fingerprint of the original. If the message and its fingerprint are delivered separately, then the recipient can check whether the message has been tampered with. However, if both the message and the fingerprint were intercepted, it is an easy matter to modify the message and then repute the fingerprint. After all, the message digest algorithms are publicly known, and they don39。 t require secret keys. In that case, the recipient of the fed message and the reputed fingerprint would never know that the message has been altered. Digital signatures solve this problem. To help you understand how digital signatures work, we explain a few concepts from the field called public key cryptography. Public key cryptography is based on the notion of a public key and private key. The idea is that you tell everyone in the world your public key. However, only you hold the private key, and it is important that you safeguard it and don39。 t release it to anyone else. The keys are matched by mathematical relationships, but the exact nature of these relationships is not important for us. (If you are interested, you can look it up in The Handbook of Applied Cryptography at The keys are quite long and plex. For example, here is a matching pair of public and 山东建筑大学毕业论文 外文文献 及译文 5 private Digital Signature Algorithm (DSA) keys. Public key: Code View: p: fca682ce8e12caba26efccf7110e526db078b05edecbcd1eb4a208f3ae1617ae01f35b91a47e6df63413c5e12ed0899bcd132acd50d99151bdc43ee737592e17 q: 962eddcc369cba8ebb260ee6b6a126d9346e38c5 g:678471b27a9cf44ee91a49c5147db1a9aaf244f05a434d6486931d2d14271b9e35030b71fd73da179069b32e2935630e1c2062354d0da20a6c416e50be794ca4 y: c0b6e67b4ac098eb1a32c5f8c4c1f0e7e6fb9d832532e27d0bdab9ca2d2a8123ce5a8018b8161a760480fadd040b927281ddb22cb9bc4df596d7de4d1b977d50 Private key: Code View: p: fca682ce8e12caba26efccf7110e526db078b05edecbcd1eb4a208f3ae1617ae01f35b91a47e6df63413c5e12ed0899bcd132acd50d99151bdc43ee737592e17 q: 962eddcc369cba8ebb260ee6b6a126d9346e38c5 g: 678471b27a9cf44ee91a49c5147db1a9aaf244f05a434d6486931d2d14271b9e35030b71fd73da179069b32e2935630e1c2062354d0da20a6c416e50be794ca4 x: 146c09f881656cc6c51f27ea6c3a91b85ed1d70a It is believed to be practically impossible to pute one key from the other. That is, even though everyone knows your public key, they can39。 t pute your private key in your lifetime, no matter how many puting resources they have available. It might seem difficult to believe that nobody can pute the private key from the public keys, but nobody has ever found an algorithm to do this for the encryption algorithms that are in mon use today. If the keys are sufficiently long, brute force—simply trying all possible keys—would require more puters than can be built from all the atoms in the solar system, crunching away for thousands of years. Of course, it is possible that someone could e up with 山东建筑大学毕业论文 外文文献 及译文 6 algorithms for puting keys that are much more clever than brute force. For example, the RSA algorithm (the encryption algorithm invented by Rivest, Shamir, and Adleman) depends on the difficulty of factoring large numbers. For the last 20 years, many of the best mathematicians have tried to e up with good factoring algorithms, but so far with no success. For that reason, most cryptographers believe that keys with a modulus of 2,000 bits or more are currently pletely safe from any attack. DSA is believed to be similarly secure. Figure 912 illustrates how the process works in practice. Suppose Alice wants to send Bob a message, and Bob wants to know this message came from Alice and not an impostor. Alice writes the message and then signs the message digest with her private key.。