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The throw away private keys below (master ed25519 & subkey curve 25519) were exported without being password encrypted.

% cat skaht_0523F5B4_Secret.asc

-----BEGIN PGP PRIVATE KEY BLOCK-----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=V0+2
-----END PGP PRIVATE KEY BLOCK-----

https://cirw.in/gpg-decoder/ (https://github.com/ConradIrwin/gpg-decoder) does a good job at identifying of breaking the the PRIVATE KEY BLOCK above into its constituent parts, but lacks functionality to properly parse the 5 packets below into their constituent parts.

PGP PRIVATE KEY BLOCK Contains 5 Packets:

  1. Secret-Key Packet (0x6):
  2. User ID Packet (0xd):
  3. Signature Packet (0x2):
  4. Secret-Subkey Packet (0x7):
  5. Signature Packet (0x2):

After removing the header & footer decorations from the skaht_0523F5B4_Secret.asc file to create skaht_0523F5B4_Secret, the raw hex data can easily be obtained.

% cat skaht_0523F5B4_Secret | bx base64-decode | bx base16-encode 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

Packets #1. Secret-Key Packet (0x6), and #4. Secret-Subkey Packet (0x7) above are of primary interest:

1) Secret-Key Packet (0x5), Tag 5:

https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-rfc4880bis-08#section-5.5.3 "5.5.3. Secret-Key Packet Formats"

9458045df0288b16092b06010401da470f0101074043997a18129856e6bd2065661e264d119ca4776874024c4ee6670b35a9d624ed000100b624cdf119dea1b4285e701a4b4d818cf99d2d44b42cd4ea391460601360fac20f7b

  • 94
  • 58 = 88 bytes are contained in the remainder of the packet
  • 04 = Version 4
  • 5df0288b = Tuesday, December 10, 2019 6:21:47 PM GMT-05:00
  • 16 = "EdDSA [RFC8032]"
  • 09 = the number of bytes that follow that representing the curve OID
  • 2b06010401da470f01 = "1.3.6.1.4.1.11591.15.1", Ed25519; is the Curve OID bytes ASN.1 ObjectIdentifier
  • 010740
  • 43997a18129856e6bd2065661e264d119ca4776874024c4ee6670b35a9d624ed = Public Master Ed25519 Key
  • 000100b624
  • cdf119dea1b4285e701a4b4d818cf99d2d44b42cd4ea391460601360fac20f7b is likely the Secret Master Ed25519 Key used for digital signatures.

4) Secret-Subkey Packet (0x7), Tag 7:

https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-rfc4880bis-08#section-5.5.1.4 "5.5.1.4. Secret-Subkey Packet (Tag 7)"

9c5d045df0288b120a2b060104019755010501010740f9df30a99049662de300a59cf97714bbbc4b6280136f8e00f73339a8d1f51019030108070000ff5b66b8367903c68450747bb8ead3863512b5d2155f4e79290289a7559160d4400f6c

  • 9c ?
  • 5d = 93 bytes are contained in the remainder of the packet
  • 04 = Version 4
  • 5df0288b = Tuesday, December 10, 2019 6:21:47 PM GMT-05:00
  • 12 = ECDH public key algorithm
  • 0a = number of bytes that follow representing the curve OID
  • 2b060104019755010501 = "1.3.6.1.4.1.3029.1.5.1", Curve25519
  • 010740 ?
  • f9df30a9 ?
  • 9049662de300a59cf97714bbbc4b6280136f8e00f73339a8d1f5101903010807 = the Public Curve25519 Subkey
  • 0000ff5b66 ?
  • b8367903c68450747bb8ead3863512b5d2155f4e79290289a7559160d4400f6c = likely the Secret Curve25519 Subkey used for Diffie-Helman key exchanges to support encrypted communication channels.

The issue I have with reading https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-rfc4880bis-08 is that the bolded highlighted fields are too difficult to translate from examining the latest Draft RFC. Can someone try to explain what the values above really map to?

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1 Answer 1

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Not trivial by any means, but the bolded script below complements the output of:

% gpg --verbose --list-packets skaht_0523F5B4_Secret.asc

% ./parse.csh skaht_0523F5B4_Secret.asc

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


1) ECC Secret-Key Packet (Tag 5): 0x94
   Raw Packet: 9458045df0288b16092b06010401da470f0101074043997a18129856e6bd2065661e264d119ca4776874024c4ee6670b35a9d624ed000100b624cdf119dea1b4285e701a4b4d818cf99d2d44b42cd4ea391460601360fac20f7b
   Packet size in bytes         : 90
   Packet body size in bytes    : 0x58 or 88
   Packet Version               : 0x04
             UNIX Epoch Time    : 0x5df0288b  or  Tue Dec 10 18:21:47 EST 2019
             Pubkey Algo index  : 0x16 -> EdDSA [RFC8032]
             OID Size in bytes  : 0x09 or 9
             Object Identifier  : 0x2b06010401da470f01 -> 1.3.6.1.4.1.11591.15.1, Ed25519
             KDF Size in bytes  : 0x01 or 1
             KDF Details        : 0x07 -> SHA2-256
             Canonical Prefix   : 0x40 -> Native point format, compressed
               Public Key       : 43997a18129856e6bd2065661e264d119ca4776874024c4ee6670b35a9d624ed
               Fingerprint Basis: 990033045df0288b16092b06010401da470f0101074043997a18129856e6bd2065661e264d119ca4776874024c4ee6670b35a9d624ed
               Fingerprint      : d94ee1e3e829ec0a1f3edac9f913b6e10523f5b4
           S2K Hash Header      : 0x00 -> Simple S2K
           S2K Hash Algorithm   : 0x01 -> SHA-1
           S2K Cipher Header    : 0x00 -> No S2K Cipher, No encryption, Cleartext
               Secret Key       : b624cdf119dea1b4285e701a4b4d818cf99d2d44b42cd4ea391460601360fac2
               Checksum         : 0x0f7b

2) User ID Packet       (Tag 13): 0xb4
   Raw Packet: b427736b6168742028746d702d323535313929203c73636f747440696e74656772696b65792e696f3e
   Packet size in bytes         : 41
   Packet body size in bytes    : 0x27 or 39
                 User ID String : skaht (tmp-25519) <[email protected]>

3) ECC Signature Packet  (Tag 2): 0x88
   Raw Packet: 88960413160a003e162104d94ee1e3e829ec0a1f3edac9f913b6e10523f5b405025df0288b021b03050901e13380050b0908070305150a09080b051602030100021e01021780000a0910f913b6e10523f5b423060100a309b6c4a8f86903d21eb8ced607ade318d9bbb8b040cc2008d4a24e86dcf2170100ee58011126799c8b55de18756369b5261d01fb62230639e99e4e0878465ae108
   Packet size in bytes         : 152
   Packet body size in bytes    : 0x96 or 150
   Packet Version               : 0x04
                 Signature Type : 0x13 -> Positive certification of a User ID and Public-Key packet.
           Public Key Algorithm : 0x16 -> EdDSA [RFC8032]
                 Hash Algorithm : 0x0a -> SHA2-512 [FIPS180] or SHA512
              HASHED DATA COUNT : 0x003e or 62
   Subpacket #1 Length in bytes : 0x16 or 22
                 Subpacket Type : 0x21 -> Issuer Fingerprint - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.28
             Fingerprint Prefix : 0x04
           Issuer's Fingerprint : 0xd94ee1e3e829ec0a1f3edac9f913b6e10523f5b4
   Subpacket #2 Length in bytes : 0x05 or 5
                 Subpacket Type : 0x02 -> Issuer Signature Creation Time - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.4
                UNIX Epoch Time : 0x5df0288b  or  Tue Dec 10 18:21:47 EST 2019
   Subpacket #3 Length in bytes : 0x02 or 2
                 Subpacket Type : 0x1b -> Key Flags - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.22
                    Hashed Data : 0x03
   Subpacket #4 Length in bytes : 0x05 or 5
                 Subpacket Type : 0x09 -> Key Expiration Time - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.6
                UNIX Epoch Time : 0x01e13380  or  Thu Dec 31 19:00:00 EST 1970
   Subpacket #5 Length in bytes : 0x05 or 5
                 Subpacket Type : 0x0b -> Preferred Symmetric Algorithms - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-9.3
                    Hashed Data : 0x09080703
   Subpacket #6 Length in bytes : 0x05 or 5
                 Subpacket Type : 0x15 -> Preferred Hash Algorithms - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-9.5
                    Hashed Data : 0x0a09080b
   Subpacket #7 Length in bytes : 0x05 or 5
                 Subpacket Type : 0x16 -> Preferred Compression Algorithms - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-9.4
                    Hashed Data : 0x02030100
   Subpacket #8 Length in bytes : 0x02 or 2
                 Subpacket Type : 0x1e -> Features - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.25
                    Hashed Data : 0x01
   Subpacket #9 Length in bytes : 0x02 or 2
                 Subpacket Type : 0x17 -> Key Server Preference - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.18
                    Hashed Data : 0x80
            UNHASHED DATA COUNT : 0x000a or 10
   Subpacket #10 Length in bytes : 0x09 or 9
                 Subpacket Type : 0x10 -> Issuer - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.5
                  Unhashed Data : 0xf913b6e10523f5b4
          signedHashValuePrefix : 0x2306
                   Delimiter #1 : 0x0100
         R Portion of Signature : a309b6c4a8f86903d21eb8ced607ade318d9bbb8b040cc2008d4a24e86dcf217
                   Delimiter #2 : 0x0100
         S Portion of Signature : ee58011126799c8b55de18756369b5261d01fb62230639e99e4e0878465ae108

4) ECC Secret-Subkey Packet (Tag 7): 0x9c
   Raw Packet: 9c5d045df0288b120a2b060104019755010501010740f9df30a99049662de300a59cf97714bbbc4b6280136f8e00f73339a8d1f51019030108070000ff5b66b8367903c68450747bb8ead3863512b5d2155f4e79290289a7559160d4400f6c
   Packet size in bytes         : 95
   Packet body size in bytes    : 0x5d or 93
   Packet Version               : 0x04
             UNIX Epoch Time    : 0x5df0288b  or  Tue Dec 10 18:21:47 EST 2019
             Pubkey Algo index  : 0x12 -> ECDH public key algorithm
             OID Size in bytes  : 0x0a or 10
             Object Identifier  : 0x2b060104019755010501 -> 1.3.6.1.4.1.3029.1.5.1, Curve25519
             KDF Size in bytes  : 0x01 or 1
             KDF Details        : 0x07 -> SHA2-256
             Canonical Prefix   : 0x40 -> Native point format, compressed
               Public Key       : f9df30a99049662de300a59cf97714bbbc4b6280136f8e00f73339a8d1f51019
       Public Key Mystery Field : 0x03010807
               Fingerprint Basis: 990038045df0288b120a2b060104019755010501010740f9df30a99049662de300a59cf97714bbbc4b6280136f8e00f73339a8d1f5101903010807
               Fingerprint      : 8517dbf00c6543587342e5b98f345dd05147c2fd
           S2K Hash Header      : 0x00 -> Simple S2K
           S2K Hash Algorithm   : 0x00 -> MD5 [HAC]
           S2K Cipher Header    : 0xff -> No S2K Cipher, No encryption, Cleartext
               Secret Key       : 5b66b8367903c68450747bb8ead3863512b5d2155f4e79290289a7559160d440
               Checksum         : 0x0f6c

5) ECC Signature Packet  (Tag 2): 0x88
   Raw Packet: 887e0418160a0026162104d94ee1e3e829ec0a1f3edac9f913b6e10523f5b405025df0288b021b0c050901e13380000a0910f913b6e10523f5b4d11500fe210ebd7c1914f0b521424b3784310877cfef5989a9787cae7e7cd0efb085517b0100aa06abc0a11e11e8a8bf2c25de3b0375f72e4368f41553132e36c22eab0e100a
   Packet size in bytes         : 128
   Packet body size in bytes    : 0x7e or 126
   Packet Version               : 0x04
                 Signature Type : 0x18 -> Subkey Binding Signature.
           Public Key Algorithm : 0x16 -> EdDSA [RFC8032]
                 Hash Algorithm : 0x0a -> SHA2-512 [FIPS180] or SHA512
              HASHED DATA COUNT : 0x0026 or 38
   Subpacket #1 Length in bytes : 0x16 or 22
                 Subpacket Type : 0x21 -> Issuer Fingerprint - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.28
             Fingerprint Prefix : 0x04
           Issuer's Fingerprint : 0xd94ee1e3e829ec0a1f3edac9f913b6e10523f5b4
   Subpacket #2 Length in bytes : 0x05 or 5
                 Subpacket Type : 0x02 -> Issuer Signature Creation Time - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.4
                UNIX Epoch Time : 0x5df0288b  or  Tue Dec 10 18:21:47 EST 2019
   Subpacket #3 Length in bytes : 0x02 or 2
                 Subpacket Type : 0x1b -> Key Flags - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.22
                    Hashed Data : 0x0c
   Subpacket #4 Length in bytes : 0x05 or 5
                 Subpacket Type : 0x09 -> Key Expiration Time - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.6
                UNIX Epoch Time : 0x01e13380  or  Thu Dec 31 19:00:00 EST 1970
            UNHASHED DATA COUNT : 0x000a or 10
   Subpacket #5 Length in bytes : 0x09 or 9
                 Subpacket Type : 0x10 -> Issuer - https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-08#section-5.2.3.5
                  Unhashed Data : 0xf913b6e10523f5b4
          signedHashValuePrefix : 0xd115
                   Delimiter #1 : 0x00fe
         R Portion of Signature : 210ebd7c1914f0b521424b3784310877cfef5989a9787cae7e7cd0efb085517b
                   Delimiter #2 : 0x0100
         S Portion of Signature : aa06abc0a11e11e8a8bf2c25de3b0375f72e4368f41553132e36c22eab0e100a
```
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