Additional opcodes

Principal Investigator: Patrick Strateman

Elements includes several new script opcodes, in addition to the ones already supported by Bitcoin:

• Elements reintroduces some safe but disabled opcodes, including string concatenation, substrings, integer shifts, and several bitwise operations.

• A new DETERMINISTICRANDOM operation which produces a random number within a range from a seed.

• A new CHECKSIGFROMSTACK operation which verifies a signature against a message on the stack, rather than the spending transaction itself.

These new opcodes have several use cases, including double-spent protection bonds, lotteries, merkle tree constructions to allow 1-of-N multisig with huge N (thousands), and probabilistic payments.