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ch19: "zooming in" data signature examples

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@ -3,4 +3,221 @@ SPDX-FileCopyrightText: 2023 The "Notes on OpenPGP" project
SPDX-License-Identifier: CC-BY-SA-4.0
-->
(zoom_sign_data)=
# Zooming in: Packet structure of data signatures
In this chapter, we'll create signatures using [Alice's private key](alice_priv) 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:
```text
$ echo "hello world" > message.txt
```
## Detached signature
We can produce a detached signature for this "hello world" message, using Alice's private signing key material:
```text
$ 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:
```text
$ 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 15:40:57 UTC (critical)
Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
Digest prefix: 97F5
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 2b 89 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 97 digest_prefix1
00000038 f5 digest_prefix2
00000039 20 salt_len
0000003a b4 c6 ed 8e 3f 08 salt
00000040 90 69 36 82 19 7d e9 df 74 18 af 92 d1 ee a3 08
00000050 0a 18 87 de 56 f1 01 a3 00 89
0000005a ef 83 32 b9 40 84 ed25519_sig
00000060 10 21 33 f4 7a e9 05 0d 5c 16 10 75 27 95 0a 32
00000070 49 e0 98 2d 0e 74 b0 f1 17 d4 3e 69 95 a7 6f b9
00000080 76 bc 22 3d ee 9c 46 e8 d5 41 12 6c c8 f5 c6 37
00000090 06 14 f5 3b a7 cd a7 ea 96 0b
```
## Inline signature
```text
$ sq sign --signer-file alice.pgp message.txt
-----BEGIN PGP MESSAGE-----
xA0DAAob0Hsk7JGhTdIByxJiAAAAAABoZWxsbyB3b3JsZArCmAYAGwoAAAApBYJl
PS6aIiEG0Hsk7JGhTdJArC1T5sip4FSUmkEiLqc4V27RnK6j3JkAAAAA2fQg3Chc
XOvRADo3I2sUdXevtp29q//4cFpY89jZSmZccCmC0rzU2cuCZTPer8IugpmpbcAT
VePYVzWPYUH/XcGJBuGNJVbKSGP2sgNqUb33XhtusK+TRiu4qxgwgOXVywwF
=AZt5
-----END PGP MESSAGE-----
```
```text
$ sq sign --signer-file alice.pgp message.txt |sq packet dump --hex
One-Pass Signature Packet, new CTB, 2 header bytes + 13 bytes
Version: 3
Type: Binary
Pk algo: Ed25519
Hash algo: SHA512
Issuer: D07B24EC91A14DD2
Last: true
00000000 c4 CTB
00000001 0d length
00000002 03 version
00000003 00 type
00000004 0a hash_algo
00000005 1b pk_algo
00000006 d0 7b 24 ec 91 a1 4d d2 issuer
0000000e 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 15:54:09 UTC (critical)
Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
Digest prefix: 89FF
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 2e a1 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 89 digest_prefix1
00000038 ff digest_prefix2
00000039 20 salt_len
0000003a f9 e8 86 74 33 55 salt
00000040 b1 23 dc 05 b2 0a 48 ff 68 83 4d 69 94 da b3 67
00000050 d2 4e 46 5d f1 0e 44 4b d9 29
0000005a 47 42 69 50 a2 85 ed25519_sig
00000060 b3 e4 35 38 72 f0 d6 68 2b 59 21 d9 1c 1a 6a 7a
00000070 92 74 6e 06 63 2b ad 23 85 97 ae 25 39 06 88 dc
00000080 8e d6 6b 6d a9 c1 16 08 e6 c4 d9 9c 6a a6 5d 50
00000090 74 aa c3 95 c4 9a b0 03 ee 03
```
## Cleartext signature
```text
$ 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-----
```
```text
$ sq sign --cleartext-signature --signer-file alice.pgp message.txt |sq packet dump --hex
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 15:56:30 UTC (critical)
Issuer Fingerprint: D07B24EC91A14DD240AC2D53E6C8A9E054949A41222EA738576ED19CAEA3DC99
Digest prefix: 53D2
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 2e 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 53 digest_prefix1
00000038 d2 digest_prefix2
00000039 20 salt_len
0000003a 9d e4 5e 3f 37 33 salt
00000040 d8 9c 70 d8 b5 e2 30 48 6c b8 2e 75 9d 7c 10 3b
00000050 42 a2 6d f4 db 96 47 d3 57 42
0000005a 58 99 2f 2c a2 35 ed25519_sig
00000060 b7 3f 63 8a 7f f1 d0 b7 5b 38 cd 92 bb e9 b5 59
00000070 9b 45 e1 0b fd d9 e7 96 4d e4 e9 5f 22 29 91 6d
00000080 85 a3 94 90 11 9d 3a 3d 32 74 a7 32 ca 73 4b 45
00000090 4f 19 a5 49 3d d8 83 0e 1b 09
```