Consistency in transaction signing is critical for successful submission of transactions to Sawtooth Lake.
Step 1: Serialize the transaction
The transaction schema describes the fields that must be present in the serialized transaction. All fields, including optional fields, must have a value set. For optional fields that are not specified, the value of the field must be set to the default value specified in the schema.
The exception to the previous rule is that the top level “Signature” field must be removed from the transaction completely. It is not sufficient simply to set the value to an empty string.
An important note is that data types must match those used in the schema. Specifically, a float must have at least one decimal point or the value will be encoded as an integer. For example, for signing purposes, 1.0 is not equivalent to 1.
All strings in the transaction including fields names and values should be encoded as Unicode.
Fields in the transaction must be ordered alpha-numerically by field name. This includes field in any contained object.
The transaction is serialized in CBOR <http://cbor.io>.
Step 2: Create the signature for the serialized transaction
The resulting serialized document is signed with the transactors private ECDSA key using the secp256k1 curve.
The signature uses a DER encoding <https://en.wikipedia.org/wiki/X.690#DER_encoding> similar to Bitcoin <https://en.bitcoin.it/wiki/Protocol_documentation#Signatures> and OpenSSL.
Step 3: Add the signature to the transaction
Set the value of the “Signature” field to the base64 encoded signature.