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

Just because alice believes a key to be valid she

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Unformatted text preview: p; Sons, Inc.) Author(s): Bruce Schneier ISBN: 0471128457 Publication Date: 01/01/96 Search this book: Go! Previous Table of Contents Next ----------- Figures 24.5 and 24.6 show messages with public-key key management (called “asymmetric” in PEM nomenclature). The headers are different. In ENCRYPTED messages, after the “DEK-Info” field comes the “Originator-Certificate” field. The certificate follows the X.509 standard (see Section 24.9). The next field is “Key-Info” with two subfields. The first subfield specifies the public-key algorithm used to encrypt the DEK; currently only RSA is supported. The next subfield is the DEK, encrypted in the originator’s public key. This is an optional field, intended to permit the originator to decrypt his own message in the event that it is returned by the mail system. The next field “Issuer-Certificate, ” is the certificate of whomever signed the Originator-Certificate. Continuing with the asymmetric key-management case, the next field is “MIC-Info.” The first subfield gives the algorithm under which the MIC was computed. The second subfield shows the algorithm under which the MIC was signed. The third subfield consists of the MIC, signed by the sender’s private key. -----BEGIN PRIVACY-ENHANCED MESSAGE----Proc-Type: 4,MIC-ONLY Content-Domain: RFC822 Originator-Certificate: MIIBlTCCAScCAWUwDQYJKoZIhvcNAQECBQAwUTELMAkGA1UEBhMCVVMxIDAeBgNV BAoTF1JTQSBEYXRhIFNlY3VyaXR5LCBJbmMuMQ8wDQYDVQQLEwZCZXRhIDExDzAN BgNVBAsTBk5PVEFSWTAeFw05MTA5MDQxODM4MTdaFw05MzA5MDMxODM4MTZaMEUx CzAJBgNVBAYTAlVTMSAwHgYDVQQKExdSU0EgRGF0YSBTZWN1cml0eSwgSW5jLjEU MBIGA1UEAxMLVGVzdCBVc2VyIDEwWTAKBgRVCAEBAgICAANLADBIAkEAwHZHl7i+ yJcqDtjJCowzTdBJrdAiLAnSC+CnnjOJELyuQiBgkGrgIh3j8/x0fM+YrsyF1u3F LZPVtzlndhYFJQIDAQABMA0GCSqGSIb3DQEBAgUAA1kACKr0PqphJYw1j+YPtcIq iWlFPuN5jJ79Khfg7ASFxskYkEMjRNZV/HZDZQEhtVaU7Jxfzs2wfX5byMp2X3U/ 5XUXGx7qusDgHQGs7Jk9W8CW1fuSWUgN4w== Issuer-Certificate: MIIB3DCCAUgCAQowDQYJKoZIhvcNAQECBQAwTzELMAkGA1UEBhMCVVMxIDAeBgNV BAo...
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