Digest
The DigestService class is a service that offers the main crypto methods for calculating transaction hashes and building Merkle trees. The default instance is passed by default to instances of classes like TransactionBuilder and as a parameter to MerkleTree.getMerkleTree(...) method. In future the default instance can be parametrized to initialize with the network default hash algorithm or just a more secure algorithm (e.g. SHA3_256). While the SHA2_256 is vulnerable to pre-image attacks, the computeNonce and componentHash methods behaviour is defined by the hashTwiceNonce and hashTwiceComponent; with SHA2_256 they both must be set to true to ensure pre-image attack won't work (and for backward compatibility), but for other algorithms like SHA3_256 that are not affected, they can and should be set to false as hashing twice would not improve security but affect performance.
Parameters
the name of the hash algorithm to be used for the instance
Properties
Functions
Return the HASH(HASH(nonce || serializedComponent)) for SHA2-256 and other algorithms loaded via JCA MessageDigest, otherwise it's defined by DigestAlgorithm.componentDigest(nonce || serializedComponent).
Compute the hash of each serialised component so as to be used as Merkle tree leaf. The resultant output (leaf) is calculated using the service's hash algorithm, thus HASH(HASH(nonce || serializedComponent)) for SHA2-256 and other algorithms loaded via JCA MessageDigest, or DigestAlgorithm.componentDigest(nonce || serializedComponent) otherwise, where nonce is computed from computeNonce.
Method to compute a nonce based on privacySalt, component group index and component internal index. SHA256d (double SHA256) is used to prevent length extension attacks.
Serialise the object and return the hash of the serialized bytes. Note that the resulting hash may not be deterministic across platform versions: serialization can produce different values if any of the types being serialized have changed, or if the version of serialization specified by the context changes.