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232 lines
11 KiB
Markdown
232 lines
11 KiB
Markdown
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<!--
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SPDX-FileCopyrightText: 2023 The "Notes on OpenPGP" project
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SPDX-License-Identifier: CC-BY-SA-4.0
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-->
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# Zooming in: Packet structure of data signatures
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In this chapter, we'll create signatures using [Alice's private key](alice-priv) material, and inspect the packet structure of those signatures.
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In some examples, we'll use a test-message that contains the string `hello world` followed by one line feed (`0x0a`) character:
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```text
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$ echo "hello world" > message.txt
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```
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## Detached signature
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We can produce a detached signature for this "hello world" message, using Alice's private signing key material:
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```text
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$ sq sign --detached --signer-file alice.pgp message.txt
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-----BEGIN PGP SIGNATURE-----
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wpgGABsKAAAAKQWCZT0tDyIhBtB7JOyRoU3SQKwtU+bIqeBUlJpBIi6nOFdu0Zyu
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o9yZAAAAANueIJCkVJ5aC1Zw485o7Y72uHPnk7ktkZyhKH2MuHjCdIHQU0qe/8bR
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0B3ywHNzLwUoqj0efYWhj6XeXa08haxUH7i50MEDjfFrPc281B0C5fiiGN4PYc76
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B8tA2/ZjsSgHCw==
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=n8EV
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-----END PGP SIGNATURE-----
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```
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And inspect the packet structure of this signature:
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```text
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$ sq packet dump --hex detached-sig.txt
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Signature Packet, new CTB, 2 header bytes + 152 bytes
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Version: 6
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Type: Binary
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Pk algo: Ed25519
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Hash algo: SHA512
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Hashed area:
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Signature creation time: 2023-10-28 15:47:27 UTC (critical)
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Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
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Digest prefix: DB9E
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Level: 0 (signature over data)
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00000000 c2 CTB
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00000001 98 length
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00000002 06 version
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00000003 00 type
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00000004 1b pk_algo
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00000005 0a hash_algo
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00000006 00 00 00 29 hashed_area_len
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0000000a 05 subpacket length
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0000000b 82 subpacket tag
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0000000c 65 3d 2d 0f sig creation time
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00000010 22 subpacket length
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00000011 21 subpacket tag
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00000012 06 version
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00000013 d0 7b 24 ec 91 a1 4d d2 40 ac 2d 53 e6 issuer fp
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00000020 c8 a9 e0 54 94 9a 41 22 2e a7 38 57 6e d1 9c ae
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00000030 a3 dc 99
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00000033 00 00 00 00 unhashed_area_len
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00000037 db digest_prefix1
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00000038 9e digest_prefix2
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00000039 20 salt_len
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0000003a 90 a4 54 9e 5a 0b salt
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00000040 56 70 e3 ce 68 ed 8e f6 b8 73 e7 93 b9 2d 91 9c
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00000050 a1 28 7d 8c b8 78 c2 74 81 d0
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0000005a 53 4a 9e ff c6 d1 ed25519_sig
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00000060 d0 1d f2 c0 73 73 2f 05 28 aa 3d 1e 7d 85 a1 8f
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00000070 a5 de 5d ad 3c 85 ac 54 1f b8 b9 d0 c1 03 8d f1
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00000080 6b 3d cd bc d4 1d 02 e5 f8 a2 18 de 0f 61 ce fa
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00000090 07 cb 40 db f6 63 b1 28 07 0b
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```
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## Inline signature
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```text
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$ sq sign --signer-file alice.pgp message.txt
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-----BEGIN PGP MESSAGE-----
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xEYGAAobIK+vlFDAK62+055LpOCoOGecp66NiyRz6M+emCLp5Nbg0Hsk7JGhTdJA
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rC1T5sip4FSUmkEiLqc4V27RnK6j3JkByxJiAAAAAABoZWxsbyB3b3JsZArCmAYA
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GwoAAAApBYJlPXuNIiEG0Hsk7JGhTdJArC1T5sip4FSUmkEiLqc4V27RnK6j3JkA
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AAAAhrggr6+UUMArrb7Tnkuk4Kg4Z5ynro2LJHPoz56YIunk1uApSiAe9CYGgqrs
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p6Ud6ARDVcOWWFhxTJK2rNULlZ9k4HPFvUT4PTrjpb4kjRAb6MDgSSclPaj14FjL
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rpr/eqQF
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=r993
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-----END PGP MESSAGE-----
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```
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```text
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$ sq packet dump --hex inline-sig.txt
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One-Pass Signature Packet, new CTB, 2 header bytes + 70 bytes
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Version: 6
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Type: Binary
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Pk algo: Ed25519
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Hash algo: SHA512
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Issuer: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
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Last: true
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00000000 c4 CTB
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00000001 46 length
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00000002 06 version
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00000003 00 type
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00000004 0a hash_algo
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00000005 1b pk_algo
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00000006 20 salt_len
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00000007 af af 94 50 c0 2b ad be d3 salt
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00000010 9e 4b a4 e0 a8 38 67 9c a7 ae 8d 8b 24 73 e8 cf
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00000020 9e 98 22 e9 e4 d6 e0
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00000027 d0 7b 24 ec 91 a1 4d d2 40 issuer
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00000030 ac 2d 53 e6 c8 a9 e0 54 94 9a 41 22 2e a7 38 57
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00000040 6e d1 9c ae a3 dc 99
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00000047 01 last
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Literal Data Packet, new CTB, 2 header bytes + 18 bytes
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Format: Binary data
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Content: "hello world\n"
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00000000 cb CTB
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00000001 12 length
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00000002 62 format
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00000003 00 filename_len
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00000004 00 00 00 00 date
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00000008 68 65 6c 6c 6f 20 77 6f hello wo
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00000010 72 6c 64 0a rld.
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Signature Packet, new CTB, 2 header bytes + 152 bytes
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Version: 6
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Type: Binary
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Pk algo: Ed25519
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Hash algo: SHA512
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Hashed area:
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Signature creation time: 2023-10-28 21:22:21 UTC (critical)
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Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
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Digest prefix: 86B8
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Level: 0 (signature over data)
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00000000 c2 CTB
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00000001 98 length
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00000002 06 version
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00000003 00 type
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00000004 1b pk_algo
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00000005 0a hash_algo
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00000006 00 00 00 29 hashed_area_len
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0000000a 05 subpacket length
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0000000b 82 subpacket tag
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0000000c 65 3d 7b 8d sig creation time
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00000010 22 subpacket length
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00000011 21 subpacket tag
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00000012 06 version
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00000013 d0 7b 24 ec 91 a1 4d d2 40 ac 2d 53 e6 issuer fp
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00000020 c8 a9 e0 54 94 9a 41 22 2e a7 38 57 6e d1 9c ae
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00000030 a3 dc 99
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00000033 00 00 00 00 unhashed_area_len
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00000037 86 digest_prefix1
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00000038 b8 digest_prefix2
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00000039 20 salt_len
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0000003a af af 94 50 c0 2b salt
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00000040 ad be d3 9e 4b a4 e0 a8 38 67 9c a7 ae 8d 8b 24
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00000050 73 e8 cf 9e 98 22 e9 e4 d6 e0
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0000005a 29 4a 20 1e f4 26 ed25519_sig
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00000060 06 82 aa ec a7 a5 1d e8 04 43 55 c3 96 58 58 71
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00000070 4c 92 b6 ac d5 0b 95 9f 64 e0 73 c5 bd 44 f8 3d
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00000080 3a e3 a5 be 24 8d 10 1b e8 c0 e0 49 27 25 3d a8
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00000090 f5 e0 58 cb ae 9a ff 7a a4 05
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```
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(cleartext)=
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## Cleartext signature
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```text
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$ sq sign --cleartext-signature --signer-file alice.pgp message.txt
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-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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hello world
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-----BEGIN PGP SIGNATURE-----
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wpgGARsKAAAAKQWCZT0vBCIhBtB7JOyRoU3SQKwtU+bIqeBUlJpBIi6nOFdu0Zyu
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o9yZAAAAANqgIHAzoRTzu/7Zuxc8Izf4r3/qSCmBfDqWzTXqmVtsSBSHACka3qbN
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eehqu8H6S0UK8V7yHbpVhExu9Hu72jWEzU/B0h9MR5gDhJPoWurx8YfyXBDsRS4y
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r13/eqMN8kfCDw==
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=Ks9w
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-----END PGP SIGNATURE-----
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```
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```text
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$ sq packet dump --hex cleartext-sig.txt
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Signature Packet, new CTB, 2 header bytes + 152 bytes
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Version: 6
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Type: Text
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Pk algo: Ed25519
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Hash algo: SHA512
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Hashed area:
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Signature creation time: 2023-10-28 15:55:48 UTC (critical)
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Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
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Digest prefix: DAA0
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Level: 0 (signature over data)
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00000000 c2 CTB
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00000001 98 length
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00000002 06 version
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00000003 01 type
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00000004 1b pk_algo
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00000005 0a hash_algo
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00000006 00 00 00 29 hashed_area_len
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0000000a 05 subpacket length
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0000000b 82 subpacket tag
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0000000c 65 3d 2f 04 sig creation time
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00000010 22 subpacket length
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00000011 21 subpacket tag
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00000012 06 version
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00000013 d0 7b 24 ec 91 a1 4d d2 40 ac 2d 53 e6 issuer fp
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00000020 c8 a9 e0 54 94 9a 41 22 2e a7 38 57 6e d1 9c ae
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00000030 a3 dc 99
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00000033 00 00 00 00 unhashed_area_len
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00000037 da digest_prefix1
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00000038 a0 digest_prefix2
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00000039 20 salt_len
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0000003a 70 33 a1 14 f3 bb salt
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00000040 fe d9 bb 17 3c 23 37 f8 af 7f ea 48 29 81 7c 3a
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00000050 96 cd 35 ea 99 5b 6c 48 14 87
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0000005a 00 29 1a de a6 cd ed25519_sig
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00000060 79 e8 6a bb c1 fa 4b 45 0a f1 5e f2 1d ba 55 84
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00000070 4c 6e f4 7b bb da 35 84 cd 4f c1 d2 1f 4c 47 98
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00000080 03 84 93 e8 5a ea f1 f1 87 f2 5c 10 ec 45 2e 32
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00000090 af 5d ff 7a a3 0d f2 47 c2 0f
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```
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