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

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Unformatted text preview: TF1JTQSBEYXRhIFNlY3VyaXR5LCBJbmMuMQ8wDQYDVQQLEwZCZXRhIDExDTAL BgNVBAsTBFRMQ0EwHhcNOTEwOTAxMDgwMDAwWhcNOTIwOTAxMDc1OTU5WjBRMQsw CQYDVQQGEwJVUzEgMB4GA1UEChMXUlNBIERhdGEgU2VjdXJpdHksIEluYy4xDzAN BgNVBAsTBkJldGEgMTEPMA0GA1UECxMGTk9UQVJZMHAwCgYEVQgBAQICArwDYgAw XwJYCsnp6lQCxYykNlODwutF/jMJ3kL+3PjYyHOwk+/9rLg6X65B/LD4bJHtO5XW cqAz/7R7XhjYCm0PcqbdzoACZtIlETrKrcJiDYoP+DkZ8k1gCk7hQHpbIwIDAQAB MA0GCSqGSIb3DQEBAgUAA38AAICPv4f9Gx/tY4+p+4DB7MV+tKZnvBoy8zgoMGOx dD2jMZ/3HsyWKWgSF0eH/AJB3qr9zosG47pyMnTf3aSy2nBO7CMxpUWRBcXUpE+x EREZd9++32ofGBIXaialnOgVUn0OzSYgugiQ077nJLDUj0hQehCizEs5wUJ35a5h MIC-Info: RSA-MD5,RSA, jV2OfH+nnXHU8bnL8kPAad/mSQlTDZlbVuxvZAOVRZ5q5+Ejl5bQvqNeqOUNQjr6 EtE7K2QDeVMCyXsdJlA8fA== LSBBIG1lc3NhZ2UgZm9yIHVzZSBpbiB0ZXN0aW5nLg0KLSBGb2xsb3dpbmcgaXMg YSBibGFuayBsaW5lOg0KDQpUaGlzIGlzIHRoZSBlbmQuDQo= -----END PRIVACY-ENHANCED MESSAGE----Figure 24.6 Example of an encapsulated MIC-ONLY message (asymmetric case). Still continuing with asymmetric key management, the next fields deal with the recipients. There are two fields for each recipient: “Recipient-ID-Asymmetric” and “Key-Info.” The “Recipient-ID-Asymmetric” field has two subfields. The first identifies the authority that issued the receiver’s public key; the second is an optional Version/Expiration subfield. The “Key-Info” field specifies the key management parameters: The first subfield identifies the algorithm used to encrypt the message and the second subfield is the DEK encrypted with the receiver’s public key. Security of PEM RSA keys in PEM can range from 508 bits to 1024 bits. This should be long enough for anyone’s security needs. A more likely attack would be against the key-management protocols. Mallory could steal your private key—don’t write it down anywhere—or attempt to fool you into accepting a bogus public key. The key certification provisions of PEM make this unlikely if everyone follows proper procedures, but people have been known to be sloppy. A more insidious attack would be for Mallory to modify the PEM implementation running on your system. This modified implementation could surreptitiously send Mallory all of...
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