2023-10-23 19:04:58 +02:00
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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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2023-10-28 17:57:50 +02:00
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(zoom_sign_data)=
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2023-10-16 15:15:35 +02:00
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# Zooming in: Packet structure of data signatures
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2023-10-28 17:57:50 +02:00
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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 15:40:57 UTC (critical)
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Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
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Digest prefix: 97F5
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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 2b 89 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 97 digest_prefix1
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00000038 f5 digest_prefix2
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00000039 20 salt_len
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0000003a b4 c6 ed 8e 3f 08 salt
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00000040 90 69 36 82 19 7d e9 df 74 18 af 92 d1 ee a3 08
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00000050 0a 18 87 de 56 f1 01 a3 00 89
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0000005a ef 83 32 b9 40 84 ed25519_sig
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00000060 10 21 33 f4 7a e9 05 0d 5c 16 10 75 27 95 0a 32
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00000070 49 e0 98 2d 0e 74 b0 f1 17 d4 3e 69 95 a7 6f b9
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00000080 76 bc 22 3d ee 9c 46 e8 d5 41 12 6c c8 f5 c6 37
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00000090 06 14 f5 3b a7 cd a7 ea 96 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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xA0DAAob0Hsk7JGhTdIByxJiAAAAAABoZWxsbyB3b3JsZArCmAYAGwoAAAApBYJl
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PS6aIiEG0Hsk7JGhTdJArC1T5sip4FSUmkEiLqc4V27RnK6j3JkAAAAA2fQg3Chc
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XOvRADo3I2sUdXevtp29q//4cFpY89jZSmZccCmC0rzU2cuCZTPer8IugpmpbcAT
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VePYVzWPYUH/XcGJBuGNJVbKSGP2sgNqUb33XhtusK+TRiu4qxgwgOXVywwF
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=AZt5
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-----END PGP MESSAGE-----
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```
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```text
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$ sq sign --signer-file alice.pgp message.txt |sq packet dump --hex
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One-Pass Signature Packet, new CTB, 2 header bytes + 13 bytes
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Version: 3
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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: D07B24EC91A14DD2
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Last: true
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00000000 c4 CTB
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00000001 0d length
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00000002 03 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 d0 7b 24 ec 91 a1 4d d2 issuer
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0000000e 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 15:54:09 UTC (critical)
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Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
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Digest prefix: 89FF
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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 2e a1 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 89 digest_prefix1
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00000038 ff digest_prefix2
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00000039 20 salt_len
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0000003a f9 e8 86 74 33 55 salt
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00000040 b1 23 dc 05 b2 0a 48 ff 68 83 4d 69 94 da b3 67
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00000050 d2 4e 46 5d f1 0e 44 4b d9 29
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0000005a 47 42 69 50 a2 85 ed25519_sig
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00000060 b3 e4 35 38 72 f0 d6 68 2b 59 21 d9 1c 1a 6a 7a
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00000070 92 74 6e 06 63 2b ad 23 85 97 ae 25 39 06 88 dc
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00000080 8e d6 6b 6d a9 c1 16 08 e6 c4 d9 9c 6a a6 5d 50
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00000090 74 aa c3 95 c4 9a b0 03 ee 03
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```
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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 sign --cleartext-signature --signer-file alice.pgp message.txt |sq packet dump --hex
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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 15:56:30 UTC (critical)
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Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
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Digest prefix: 53D2
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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 2e 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 53 digest_prefix1
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00000038 d2 digest_prefix2
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00000039 20 salt_len
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0000003a 9d e4 5e 3f 37 33 salt
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00000040 d8 9c 70 d8 b5 e2 30 48 6c b8 2e 75 9d 7c 10 3b
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00000050 42 a2 6d f4 db 96 47 d3 57 42
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0000005a 58 99 2f 2c a2 35 ed25519_sig
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00000060 b7 3f 63 8a 7f f1 d0 b7 5b 38 cd 92 bb e9 b5 59
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00000070 9b 45 e1 0b fd d9 e7 96 4d e4 e9 5f 22 29 91 6d
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00000080 85 a3 94 90 11 9d 3a 3d 32 74 a7 32 ca 73 4b 45
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00000090 4f 19 a5 49 3d d8 83 0e 1b 09
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```
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