Add type-specific usage documentation. (#374)

Signed-off-by: Dan Lorenc <lorenc.d@gmail.com>

README.md

@@ -35,6 +35,10 @@ Please reach out via the [mailing list](https://groups.google.com/g/sigstore-dev
 If you have production use-cases in mind, again - please reach out over email via the [mailing list](https://groups.google.com/g/sigstore-dev).
 We are interested in helping on board you!
 
+### Usage
+
+For examples of uploading signatures for all the supported types to rekor, see [the types documentation](types.md).
+
 ### Auditing the Instance
 
 We run a job to publish the latest Signed Tree Hashes on GCS.

types.md

+# Signing and Uploading Other Types
+
+This documentation contains information on how to sign and upload data in different pluggable types.
+
+## Minisign
+
+Create a keypair with something like:
+
+```shell
+$ minisign -G
+Please enter a password to protect the secret key.
+
+Password:
+Password (one more time):
+Deriving a key from the password in order to encrypt the secret key... done
+
+The secret key was saved as /Users/dlorenc/.minisign/minisign.key - Keep it secret!
+The public key was saved as minisign.pub - That one can be public.
+
+Files signed using this key pair can be verified with the following command:
+
+minisign -Vm <file> -P RWSzQI7+S6M0c4yReOwcDZ2petL8pAZsrNfkdyqr0V7j/HGafpjdKZQm
+```
+
+Sign a file:
+
+```shell
+$ minisign -S -m README.md
+Password:
+Deriving a key from the password and decrypting the secret key... done
+```
+
+Upload to rekor:
+
+```shell
+$ rekor-cli upload --artifact README.md --signature README.md.minisig --pki-format=minisign --public-key=minisign.pub
+Created entry at index 5895, available at: https://rekor.sigstore.dev/api/v1/log/entries/008bfbbaa8f473a0b17cba5f8078d2c08410bca55f01d2ec71860795ef823b36
+```
+
+Look at the entry with:
+
+```shell
+ $ ./rekor-cli get --uuid=008bfbbaa8f473a0b17cba5f8078d2c08410bca55f01d2ec71860795ef823b36
+LogID: c0d23d6ad406973f9559f3ba2d1ca01f84147d8ffc5b8445c224f98b9591801d
+Index: 5895
+IntegratedTime: 2021-07-14T01:39:50Z
+UUID: 008bfbbaa8f473a0b17cba5f8078d2c08410bca55f01d2ec71860795ef823b36
+Body: {
+  "RekordObj": {
+    "data": {
+      "hash": {
+        "algorithm": "sha256",
+        "value": "3d80236772ca7c5405e398a4d685e715859260a8733070b86de7322e233c68d2"
+      }
+    },
+    "signature": {
+      "content": "dW50cnVzdGVkIGNvbW1lbnQ6ClJXU3pRSTcrUzZNMGMrNUcxbVZzcmw2dmgvYi91VjlxclJySWpxd21abDFKYjZhTGJ2U1NWUzdObDNvUmpVTUdHUWpLVlEyd2JnMnJxNDZxdDdPTHE3L1c3Z2liMlo5Rzh3az0=",
+      "format": "minisign",
+      "publicKey": {
+        "content": "akpGNDdCd05uYWw2MHZ5a0JteXMxK1IzS3F2Ulh1UDhjWnArbU4wcGxDWT0="
+      }
+    }
+  }
+}
+```
+
+## SSH
+
+Generate a keypair with:
+
+```shell
+ssh-keygen -C test@rekor.dev -t ed25519 -f id_ed25519
+Generating public/private ed25519 key pair.
+Enter passphrase (empty for no passphrase):
+Enter same passphrase again:
+Your identification has been saved in id_ed25519.
+Your public key has been saved in id_ed25519.pub.
+The key fingerprint is:
+SHA256:73u0etmm2h7BehcLbjrwXqXe193k5R5Uz0Lnl83nTt4 test@rekor.dev
+The key's randomart image is:
++--[ED25519 256]--+
+|                 |
+|                 |
+|              . o|
+|           . . ==|
+|        S   + +oO|
+|        .. o.=.==|
+|         oo.B+o=B|
+|         .oB=+o+X|
+|         .BO=o.oE|
++----[SHA256]-----+
+```
+
+Sign a file with:
+
+```shell
+$ ssh-keygen -Y sign -n file -f id_ed25519 README.md
+Enter passphrase:
+Signing file README.md
+Write signature to README.md.sig
+```
+
+Upload it to rekor with:
+
+```shell
+$ rekor-cli upload --artifact README.md --signature README.md.sig --pki-format=ssh --public-key=id_ed25519.pub
+Created entry at index 5896, available at: https://rekor.sigstore.dev/api/v1/log/entries/0e81b4d9299e2609e45b5c453a4c0e7820ac74e02c4935a8b830d104632fd2d
+```
+
+Look at the entry with:
+
+```shell
+$ rekor-cli get --uuid=0e81b4d9299e2609e45b5c453a4c0e7820ac74e02c4935a8b830d104632fd2d1
+LogID: c0d23d6ad406973f9559f3ba2d1ca01f84147d8ffc5b8445c224f98b9591801d
+Index: 5896
+IntegratedTime: 2021-07-14T01:45:06Z
+UUID: 0e81b4d9299e2609e45b5c453a4c0e7820ac74e02c4935a8b830d104632fd2d1
+Body: {
+  "RekordObj": {
+    "data": {
+      "hash": {
+        "algorithm": "sha256",
+        "value": "3d80236772ca7c5405e398a4d685e715859260a8733070b86de7322e233c68d2"
+      }
+    },
+    "signature": {
+      "content": "LS0tLS1CRUdJTiBTU0ggU0lHTkFUVVJFLS0tLS0KVTFOSVUwbEhBQUFBQVFBQUFETUFBQUFMYzNOb0xXVmtNalUxTVRrQUFBQWdqNnhOWHFWdFJQb2JOaHg5TXNnbQp4Q2lYMlo3VFh5QXcyRHZpN0k1Nzdia0FBQUFFWm1sc1pRQUFBQUFBQUFBR2MyaGhOVEV5QUFBQVV3QUFBQXR6CmMyZ3RaV1F5TlRVeE9RQUFBRUM1N2xCUGtjWlF2K2RDOG1HMEd4ajZoeUVXOUtPZVVtN21WdFVicURSTDdramoKS1pTakYxaVFVcWVpUVQ4Z2ZKbGVyZVhhUmVMamZoR2FUN0llRENrRQotLS0tLUVORCBTU0ggU0lHTkFUVVJFLS0tLS0K",
+      "format": "ssh",
+      "publicKey": {
+        "content": "c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSUkrc1RWNmxiVVQ2R3pZY2ZUTElKc1FvbDltZTAxOGdNTmc3NHV5T2UrMjUK"
+      }
+    }
+  }
+}
+```
+
+## PKIX/X509
+
+Generate a keypair with:
+
+```shell
+$ openssl ecparam -genkey -name prime256v1 > ec_private.pem
+$ openssl ec -in ec_private.pem -pubout > ec_public.pem
+read EC key
+writing EC key
+```
+
+Sign the file with:
+
+```shell
+$ openssl dgst -sha256 -sign ec_private.pem -out README.md.sig README.md
+```
+
+Upload it to rekor with:
+
+```shell
+$ ./rekor-cli upload --artifact README.md --signature README.md.sig --pki-format=x509 --public-key=ec_public.pem
+Created entry at index 5897, available at: https://rekor.sigstore.dev/api/v1/log/entries/31a51c1bc20da83b66b2f24899184b85dbf8261c2de8571479165619ad87cd5d
+```
+
+View the entry with:
+
+```shell
+$ rekor-cli get --uuid=31a51c1bc20da83b66b2f24899184b85dbf8261c2de8571479165619ad87cd5d
+LogID: c0d23d6ad406973f9559f3ba2d1ca01f84147d8ffc5b8445c224f98b9591801d
+Index: 5897
+IntegratedTime: 2021-07-14T01:49:54Z
+UUID: 31a51c1bc20da83b66b2f24899184b85dbf8261c2de8571479165619ad87cd5d
+Body: {
+  "RekordObj": {
+    "data": {
+      "hash": {
+        "algorithm": "sha256",
+        "value": "3d80236772ca7c5405e398a4d685e715859260a8733070b86de7322e233c68d2"
+      }
+    },
+    "signature": {
+      "content": "MEUCICwZpVU/3fnWSZkejA8R2j/t5futtl5Co3CDj7k6J6PwAiEA75Cn2txgpg/KjsOitSKsydL3D6cQIf7NQJtsmvsRTRQ=",
+      "format": "x509",
+      "publicKey": {
+        "content": "LS0tLS1CRUdJTiBQVUJMSUMgS0VZLS0tLS0KTUZrd0V3WUhLb1pJemowQ0FRWUlLb1pJemowREFRY0RRZ0FFYzJKUkJZbS9OQVo5ZHhhUnNWV05mdTcxV3B5TAo2cGx4L1hsZnNVTlM2SmcrWEhEVmpsaVNBNHV2ZEQ4ZW5XdUhNdWQybS9WdEVQaDZYT0M3bjR0aCtnPT0KLS0tLS1FTkQgUFVCTElDIEtFWS0tLS0tCg=="
+      }
+    }
+  }
+}
+```
+
+### PGP
+
+TODO
+
+## RPM
+
+TODO
+
+## Alpine
+
+TODO
+
+## RPM
+
+TODO
+
+## TSR
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