28. Zooming in: Packet structure of data signatures¶
In this chapter, we’ll create signatures using Alice’s private key material, and inspect the packet structure of those signatures.
In some examples, we’ll use a test-message that contains the string hello world followed by one line feed (0x0a) character:
$ echo "hello world" > message.txt
28.1. Detached signature¶
We can produce a detached signature for this “hello world” message, using Alice’s private signing key material:
$ sq sign --detached --signer-file alice.pgp message.txt
-----BEGIN PGP SIGNATURE-----
wpgGABsKAAAAKQWCZT0tDyIhBtB7JOyRoU3SQKwtU+bIqeBUlJpBIi6nOFdu0Zyu
o9yZAAAAANueIJCkVJ5aC1Zw485o7Y72uHPnk7ktkZyhKH2MuHjCdIHQU0qe/8bR
0B3ywHNzLwUoqj0efYWhj6XeXa08haxUH7i50MEDjfFrPc281B0C5fiiGN4PYc76
B8tA2/ZjsSgHCw==
=n8EV
-----END PGP SIGNATURE-----
And inspect the packet structure of this signature:
$ sq packet dump --hex detached-sig.txt
Signature Packet, new CTB, 2 header bytes + 152 bytes
Version: 6
Type: Binary
Pk algo: Ed25519
Hash algo: SHA512
Hashed area:
Signature creation time: 2023-10-28 15:47:27 UTC (critical)
Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
Digest prefix: DB9E
Level: 0 (signature over data)
00000000 c2 CTB
00000001 98 length
00000002 06 version
00000003 00 type
00000004 1b pk_algo
00000005 0a hash_algo
00000006 00 00 00 29 hashed_area_len
0000000a 05 subpacket length
0000000b 82 subpacket tag
0000000c 65 3d 2d 0f sig creation time
00000010 22 subpacket length
00000011 21 subpacket tag
00000012 06 version
00000013 d0 7b 24 ec 91 a1 4d d2 40 ac 2d 53 e6 issuer fp
00000020 c8 a9 e0 54 94 9a 41 22 2e a7 38 57 6e d1 9c ae
00000030 a3 dc 99
00000033 00 00 00 00 unhashed_area_len
00000037 db digest_prefix1
00000038 9e digest_prefix2
00000039 20 salt_len
0000003a 90 a4 54 9e 5a 0b salt
00000040 56 70 e3 ce 68 ed 8e f6 b8 73 e7 93 b9 2d 91 9c
00000050 a1 28 7d 8c b8 78 c2 74 81 d0
0000005a 53 4a 9e ff c6 d1 ed25519_sig
00000060 d0 1d f2 c0 73 73 2f 05 28 aa 3d 1e 7d 85 a1 8f
00000070 a5 de 5d ad 3c 85 ac 54 1f b8 b9 d0 c1 03 8d f1
00000080 6b 3d cd bc d4 1d 02 e5 f8 a2 18 de 0f 61 ce fa
00000090 07 cb 40 db f6 63 b1 28 07 0b
28.2. Inline signature¶
$ sq sign --signer-file alice.pgp message.txt
-----BEGIN PGP MESSAGE-----
xEYGAAobIK+vlFDAK62+055LpOCoOGecp66NiyRz6M+emCLp5Nbg0Hsk7JGhTdJA
rC1T5sip4FSUmkEiLqc4V27RnK6j3JkByxJiAAAAAABoZWxsbyB3b3JsZArCmAYA
GwoAAAApBYJlPXuNIiEG0Hsk7JGhTdJArC1T5sip4FSUmkEiLqc4V27RnK6j3JkA
AAAAhrggr6+UUMArrb7Tnkuk4Kg4Z5ynro2LJHPoz56YIunk1uApSiAe9CYGgqrs
p6Ud6ARDVcOWWFhxTJK2rNULlZ9k4HPFvUT4PTrjpb4kjRAb6MDgSSclPaj14FjL
rpr/eqQF
=r993
-----END PGP MESSAGE-----
$ sq packet dump --hex inline-sig.txt
One-Pass Signature Packet, new CTB, 2 header bytes + 70 bytes
Version: 6
Type: Binary
Pk algo: Ed25519
Hash algo: SHA512
Issuer: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
Last: true
00000000 c4 CTB
00000001 46 length
00000002 06 version
00000003 00 type
00000004 0a hash_algo
00000005 1b pk_algo
00000006 20 salt_len
00000007 af af 94 50 c0 2b ad be d3 salt
00000010 9e 4b a4 e0 a8 38 67 9c a7 ae 8d 8b 24 73 e8 cf
00000020 9e 98 22 e9 e4 d6 e0
00000027 d0 7b 24 ec 91 a1 4d d2 40 issuer
00000030 ac 2d 53 e6 c8 a9 e0 54 94 9a 41 22 2e a7 38 57
00000040 6e d1 9c ae a3 dc 99
00000047 01 last
Literal Data Packet, new CTB, 2 header bytes + 18 bytes
Format: Binary data
Content: "hello world\n"
00000000 cb CTB
00000001 12 length
00000002 62 format
00000003 00 filename_len
00000004 00 00 00 00 date
00000008 68 65 6c 6c 6f 20 77 6f hello wo
00000010 72 6c 64 0a rld.
Signature Packet, new CTB, 2 header bytes + 152 bytes
Version: 6
Type: Binary
Pk algo: Ed25519
Hash algo: SHA512
Hashed area:
Signature creation time: 2023-10-28 21:22:21 UTC (critical)
Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
Digest prefix: 86B8
Level: 0 (signature over data)
00000000 c2 CTB
00000001 98 length
00000002 06 version
00000003 00 type
00000004 1b pk_algo
00000005 0a hash_algo
00000006 00 00 00 29 hashed_area_len
0000000a 05 subpacket length
0000000b 82 subpacket tag
0000000c 65 3d 7b 8d sig creation time
00000010 22 subpacket length
00000011 21 subpacket tag
00000012 06 version
00000013 d0 7b 24 ec 91 a1 4d d2 40 ac 2d 53 e6 issuer fp
00000020 c8 a9 e0 54 94 9a 41 22 2e a7 38 57 6e d1 9c ae
00000030 a3 dc 99
00000033 00 00 00 00 unhashed_area_len
00000037 86 digest_prefix1
00000038 b8 digest_prefix2
00000039 20 salt_len
0000003a af af 94 50 c0 2b salt
00000040 ad be d3 9e 4b a4 e0 a8 38 67 9c a7 ae 8d 8b 24
00000050 73 e8 cf 9e 98 22 e9 e4 d6 e0
0000005a 29 4a 20 1e f4 26 ed25519_sig
00000060 06 82 aa ec a7 a5 1d e8 04 43 55 c3 96 58 58 71
00000070 4c 92 b6 ac d5 0b 95 9f 64 e0 73 c5 bd 44 f8 3d
00000080 3a e3 a5 be 24 8d 10 1b e8 c0 e0 49 27 25 3d a8
00000090 f5 e0 58 cb ae 9a ff 7a a4 05
28.3. Cleartext signature¶
$ sq sign --cleartext-signature --signer-file alice.pgp message.txt
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
hello world
-----BEGIN PGP SIGNATURE-----
wpgGARsKAAAAKQWCZT0vBCIhBtB7JOyRoU3SQKwtU+bIqeBUlJpBIi6nOFdu0Zyu
o9yZAAAAANqgIHAzoRTzu/7Zuxc8Izf4r3/qSCmBfDqWzTXqmVtsSBSHACka3qbN
eehqu8H6S0UK8V7yHbpVhExu9Hu72jWEzU/B0h9MR5gDhJPoWurx8YfyXBDsRS4y
r13/eqMN8kfCDw==
=Ks9w
-----END PGP SIGNATURE-----
$ sq packet dump --hex cleartext-sig.txt
Signature Packet, new CTB, 2 header bytes + 152 bytes
Version: 6
Type: Text
Pk algo: Ed25519
Hash algo: SHA512
Hashed area:
Signature creation time: 2023-10-28 15:55:48 UTC (critical)
Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
Digest prefix: DAA0
Level: 0 (signature over data)
00000000 c2 CTB
00000001 98 length
00000002 06 version
00000003 01 type
00000004 1b pk_algo
00000005 0a hash_algo
00000006 00 00 00 29 hashed_area_len
0000000a 05 subpacket length
0000000b 82 subpacket tag
0000000c 65 3d 2f 04 sig creation time
00000010 22 subpacket length
00000011 21 subpacket tag
00000012 06 version
00000013 d0 7b 24 ec 91 a1 4d d2 40 ac 2d 53 e6 issuer fp
00000020 c8 a9 e0 54 94 9a 41 22 2e a7 38 57 6e d1 9c ae
00000030 a3 dc 99
00000033 00 00 00 00 unhashed_area_len
00000037 da digest_prefix1
00000038 a0 digest_prefix2
00000039 20 salt_len
0000003a 70 33 a1 14 f3 bb salt
00000040 fe d9 bb 17 3c 23 37 f8 af 7f ea 48 29 81 7c 3a
00000050 96 cd 35 ea 99 5b 6c 48 14 87
0000005a 00 29 1a de a6 cd ed25519_sig
00000060 79 e8 6a bb c1 fa 4b 45 0a f1 5e f2 1d ba 55 84
00000070 4c 6e f4 7b bb da 35 84 cd 4f c1 d2 1f 4c 47 98
00000080 03 84 93 e8 5a ea f1 f1 87 f2 5c 10 ec 45 2e 32
00000090 af 5d ff 7a a3 0d f2 47 c2 0f
