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

Someone might sign messages with a 2048 bit key

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Unformatted text preview: k are secure against brute-force attacks costing millions of dollars and taking millions of years. If an adversary can recover your key by taking a bag of shredded documents from your trash and paying 100 unemployed workers in some backwater country ten cents per hour for a year to piece the shredded pages together, that would be $26,000 well spent. If the key is in a hardware EEPROM, the key should be overwritten multiple times. If the key is in a hardware EPROM or PROM, the chip should be smashed into tiny bits and scattered to the four winds. If the key is stored on a computer disk, the actual bits of the storage should be overwritten multiple times (see Section 10.9) or the disk should be shredded. A potential problem is that, in a computer, keys can be easily copied and stored in multiple locations. Any computer that does its own memory management, constantly swapping programs in and out of memory, exacerbates the problem. There is no way to ensure that successful key erasure has taken place in the computer, especially if the computer’s operating system controls the erasure process. The more paranoid among you should consider writing a special erasure program that scans all disks looking for copies of the key’s bit pattern on unused blocks and then erases those blocks. Also remember to erase the contents of any temporary, or “swap,” files. 8.12 Public-Key Key Management Public-key cryptography makes key management easier, but it has its own unique problems. Each person has only one public key, regardless of the number of people on the network. If Alice wants to send a message to Bob, she has to get Bob’s public key. She can go about this several ways: — She can get it from Bob. — She can get it from a centralized database. — She can get it from her own private database. Section 2.5 discussed a number of possible attacks against public-key cryptography, based on Mallory substituting his key for Bob’s. The scenario is that Alice wants to send a message to Bob. She goes to the public-key databa...
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This note was uploaded on 10/18/2010 for the course MATH CS 301 taught by Professor Aliulger during the Fall '10 term at Koç University.

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