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

Decryption is just as easy using secret key x and

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Unformatted text preview: anies... have committed millions of dollars to RSA. We have concern over the interoperability and support of two different standards, as that situation will lead to added costs, delays in deployment, and complication.... Many companies wanted NIST to adopt the ISO 9796, the international digital signature standard that uses RSA [762]. While this is a valid complaint, it is not a sufficient justification to make it a standard. A royalty-free standard would better serve the U.S. public interest. 5. The DSA selection process was not public; sufficient time for analysis has not been provided. First NIST claimed that they designed the DSA; then they admitted that NSA helped them. Finally, they confirmed that NSA designed the algorithm. This worries many people; the NSA doesn’t inspire trust. Even so, the algorithm is public and available for analysis; and NIST extended the time for analysis and comment. 6. DSA may infringe on other patents. It may. This will be discussed in the section on patent issues. 7. The key size is too small. This was the only valid criticism of DSS. The original implementation set the modulus at 512 bits [1149]. Since the algorithm gets its security from the difficulty of computing discrete logs in that modulus, this worried most cryptographers. There have since been advances in the problem of calculating discrete logarithms in a finite field, and 512 bits is too short for long-term security (see Section 7.2). According to Brian LaMacchia and Andrew Odlyzko, “...even 512-bit primes appear to offer only marginal security...” [934]. In response to this criticism, NIST made the key size variable, from 512 bits to 1024 bits. Not great, but better. On May 19, 1994, the standard was finally issued [1154]. The issuing statement said [542]: This standard is applicable to all Federal departments and agencies for the protection of unclassified information.... This standard shall be used in designing and implementing public-key based signature schemes which Federal departments and agencies operate or which...
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