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4.6 Summary of Encapsulated Header Fields Connected: An Internet Encyclopedia
4.6 Summary of Encapsulated Header Fields

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Next: 4.6.1 Per-Message Encapsulated Header Fields

4.6 Summary of Encapsulated Header Fields

4.6 Summary of Encapsulated Header Fields

This section defines the syntax and semantics of the encapsulated header fields to be added to messages in the course of privacy enhancement processing.

The fields are presented in three groups. Normally, the groups will appear in encapsulated headers in the order in which they are shown, though not all fields in each group will appear in all messages. The following figures show the appearance of small example encapsulated messages. Figure 2 assumes the use of symmetric cryptography for key management. Figure 3 illustrates an example encapsulated ENCRYPTED message in which asymmetric key management is used.

   -----BEGIN PRIVACY-ENHANCED MESSAGE-----
   Proc-Type: 4,ENCRYPTED
   Content-Domain: RFC822
   DEK-Info: DES-CBC,F8143EDE5960C597
   Originator-ID-Symmetric: linn@zendia.enet.dec.com,,
   Recipient-ID-Symmetric: linn@zendia.enet.dec.com,ptf-kmc,3
   Key-Info: DES-ECB,RSA-MD2,9FD3AAD2F2691B9A,
             B70665BB9BF7CBCDA60195DB94F727D3
   Recipient-ID-Symmetric: pem-dev@tis.com,ptf-kmc,4
   Key-Info: DES-ECB,RSA-MD2,161A3F75DC82EF26,
             E2EF532C65CBCFF79F83A2658132DB47

   LLrHB0eJzyhP+/fSStdW8okeEnv47jxe7SJ/iN72ohNcUk2jHEUSoH1nvNSIWL9M
   8tEjmF/zxB+bATMtPjCUWbz8Lr9wloXIkjHUlBLpvXR0UrUzYbkNpk0agV2IzUpk
   J6UiRRGcDSvzrsoK+oNvqu6z7Xs5Xfz5rDqUcMlK1Z6720dcBWGGsDLpTpSCnpot
   dXd/H5LMDWnonNvPCwQUHt==
   -----END PRIVACY-ENHANCED MESSAGE-----

          Example Encapsulated Message (Symmetric Case)
                            Figure 2

Figure 4 illustrates an example encapsulated MIC-ONLY message in which asymmetric key management is used; since no per-recipient keys are involved in preparation of asymmetric-case MIC-ONLY messages, this example should be processable for test purposes by arbitrary PEM implementations.

Fully-qualified domain names (FQDNs) for hosts, appearing in the mailbox names found in entity identifier subfields of "Originator- ID-Symmetric:" and "Recipient-ID-Symmetric:" fields, are processed in a case-insensitive fashion. Unless specified to the contrary, other field arguments (including the user name components of mailbox names) are to be processed in a case-sensitive fashion.

In most cases, numeric quantities are represented in header fields as contiguous strings of hexadecimal digits, where each digit is represented by a character from the ranges "0"-"9" or upper case "A"-"F". Since public-key certificates and quantities encrypted

   -----BEGIN PRIVACY-ENHANCED MESSAGE-----
   Proc-Type: 4,ENCRYPTED
   Content-Domain: RFC822
   DEK-Info: DES-CBC,BFF968AA74691AC1
   Originator-Certificate:
    MIIBlTCCAScCAWUwDQYJKoZIhvcNAQECBQAwUTELMAkGA1UEBhMCVVMxIDAeBgNV
    BAoTF1JTQSBEYXRhIFNlY3VyaXR5LCBJbmMuMQ8wDQYDVQQLEwZCZXRhIDExDzAN
    BgNVBAsTBk5PVEFSWTAeFw05MTA5MDQxODM4MTdaFw05MzA5MDMxODM4MTZaMEUx
    CzAJBgNVBAYTAlVTMSAwHgYDVQQKExdSU0EgRGF0YSBTZWN1cml0eSwgSW5jLjEU
    MBIGA1UEAxMLVGVzdCBVc2VyIDEwWTAKBgRVCAEBAgICAANLADBIAkEAwHZHl7i+
    yJcqDtjJCowzTdBJrdAiLAnSC+CnnjOJELyuQiBgkGrgIh3j8/x0fM+YrsyF1u3F
    LZPVtzlndhYFJQIDAQABMA0GCSqGSIb3DQEBAgUAA1kACKr0PqphJYw1j+YPtcIq
    iWlFPuN5jJ79Khfg7ASFxskYkEMjRNZV/HZDZQEhtVaU7Jxfzs2wfX5byMp2X3U/
    5XUXGx7qusDgHQGs7Jk9W8CW1fuSWUgN4w==
   Key-Info: RSA,
    I3rRIGXUGWAF8js5wCzRTkdhO34PTHdRZY9Tuvm03M+NM7fx6qc5udixps2Lng0+
    wGrtiUm/ovtKdinz6ZQ/aQ==
   Issuer-Certificate:
    MIIB3DCCAUgCAQowDQYJKoZIhvcNAQECBQAwTzELMAkGA1UEBhMCVVMxIDAeBgNV
    BAoTF1JTQSBEYXRhIFNlY3VyaXR5LCBJbmMuMQ8wDQYDVQQLEwZCZXRhIDExDTAL
    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,
    UdFJR8u/TIGhfH65ieewe2lOW4tooa3vZCvVNGBZirf/7nrgzWDABz8w9NsXSexv
    AjRFbHoNPzBuxwmOAFeA0HJszL4yBvhG
   Recipient-ID-Asymmetric:
    MFExCzAJBgNVBAYTAlVTMSAwHgYDVQQKExdSU0EgRGF0YSBTZWN1cml0eSwgSW5j
    LjEPMA0GA1UECxMGQmV0YSAxMQ8wDQYDVQQLEwZOT1RBUlk=,
    66
   Key-Info: RSA,
    O6BS1ww9CTyHPtS3bMLD+L0hejdvX6Qv1HK2ds2sQPEaXhX8EhvVphHYTjwekdWv
    7x0Z3Jx2vTAhOYHMcqqCjA==

   qeWlj/YJ2Uf5ng9yznPbtD0mYloSwIuV9FRYx+gzY+8iXd/NQrXHfi6/MhPfPF3d
   jIqCJAxvld2xgqQimUzoS1a4r7kQQ5c/Iua4LqKeq3ciFzEv/MbZhA==
   -----END PRIVACY-ENHANCED MESSAGE-----

    Example Encapsulated ENCRYPTED Message (Asymmetric Case)
                            Figure 3

using asymmetric algorithms are large in size, use of a more space- efficient encoding technique is appropriate for such quantities, and the encoding mechanism defined in Section 4.3.2.4 of this RFC, representing 6 bits per printed character, is adopted for this purpose.

Encapsulated headers of PEM messages are folded using whitespace per RFC 822 header folding conventions; no PEM-specific conventions are defined for encapsulated header folding. The example shown in Figure 4 shows (in its "MIC-Info:" field) an asymmetrically encrypted quantity in its printably encoded representation, illustrating the use of RFC 822 folding.

In contrast to the encapsulated header representations defined in RFC 1113 and its precursors, the field identifiers adopted in this RFC do not begin with the prefix "X-" (for example, the field previously denoted "X-Key-Info:" is now denoted "Key-Info:") and such prefixes are not to be emitted by implementations conformant to this RFC. To simplify transition and interoperability with earlier implementations, it is suggested that implementations based on this RFC accept incoming encapsulated header fields carrying the "X-" prefix and act on such fields as if the "X-" were not present.

   -----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
    BAoTF1JTQSBEYXRhIFNlY3VyaXR5LCBJbmMuMQ8wDQYDVQQLEwZCZXRhIDExDTAL
    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-----

     Example Encapsulated MIC-ONLY Message (Asymmetric Case)
                            Figure 4


Next: 4.6.1 Per-Message Encapsulated Header Fields

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