Add crypto consensus test infrastructure

This adds the commands

```
rolling-shutter crypto testdata [output_file]
rolling-shutter crypto jsontests -f input_file
```

that will generate or execute tests for the methods

```
shcrypto.Encrypt
shcrypto.EncryptedMessage.Decrypt
shcrypto.VerifyEpochSecret
```

The output from `testdata` is a json file with test specifications
similar to
```
[
  {
    "name": "decryption 2",
    "id": "3",
    "description": "A 1 byte message.",
    "type": "decryption",
    "test_data": {
      "cipher": "0x20b1bd1817ead1ccf50b04ef9b77fac4c6d9b60b63436b54483f642128df31fb204d9460355ab724eb255fba7459b170306f42fd2dd7d5acc43b9c96287602760ed9138b682a195489749669573a8492b615e9c1b5185fc272a1268fad8c035e03162b507b968a34d211f168e5c1e9e3df975974e242d36d6be99ba88dcb0944fdcb3887b2fda72ce25f0dfcd8ef6d7de49a1c4d66de07ed591aa84caf406c42c1c88417d5cee83b3ef00da832d3ed35017ddc602c3a24c7deac3af725f27266",
      "epoch_secret_key": "0x144e428af1602d58bfb9a12bb31597f45c6c2c9d227b7a6d3f35f37d333548eb0888206e52d7cb2c6b1de7770fc2ce475a08e6cf4e95a608ec5bd93efafed6f3",
      "expected": "0x11"
    }
  },
...
]
```

There are three test types corresponding to the crypto methods from
above: `decryption, encryption, verification`.

For `decryption` and `encryption` tests, an `expected` value of `0x`
means that the result should be empty (i.e. a failure,
with the exception of the special case of an empty encrypted message).

For verification tests the `expected` value is a boolean `true/false`.

Author: konradkonrad

rolling-shutter/cmd/cryptocmd/cryptocmd.go

@@ -20,19 +20,23 @@ var (
 	epochIDFlag       string
 	sigmaFlag         string
 	threshold         uint64
+	filename          string
 )
 
 func Cmd() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "crypto",
 		Short: "CLI tool to access crypto functions",
 		Long: `This command provides utility functions to manually encrypt messages with an eon
-key, decrypt them with a decryption key, and check that a decryption key is correct.`,
+key, decrypt them with a decryption key, and check that a decryption key is correct. It also hosts
+a tool to generate and run crypto tests in a JSON formatted collection.`,
 	}
 	cmd.AddCommand(encryptCmd())
 	cmd.AddCommand(decryptCmd())
 	cmd.AddCommand(verifyKeyCmd())
 	cmd.AddCommand(aggregateCmd())
+	cmd.AddCommand(GenerateTestdata())
+	cmd.AddCommand(RunJSONTests())
 	return cmd
 }