Any Innovations in altcoin tech for Bitcoin’s Script language? [closed]

Question

Bitcoin’s Script is the forth-like, non-Turing complete language used for transactions. However, in practice, a very limited number of kinds of scripts are allowed, a number of opcodes have been disabled, and even a number of bugs in script have to be replicated to maintain consensus.

Have there been any innovations by the altcoin community, in their forks of Bitcoin’s Script? Any with non-secp256k1 crypto? Any with more functional bignum / arbitrary integer functionality that can do cryptographic primitives? Any that add Turing complete functionality?

Answer 1

Bitcoin Cash is a code and blockhain fork (blocks 0 to 478558 are the same on both blockchains) which did the following upgrades to Bitcoin Script VM:

• 2017 Malleability fixes
  • Mandatory use of SCRIPT_VERIFY_STRICTENC
  • Enforcement of LOW_S signatures and NULLFAIL (BIP-0146)
• 2018
  • OP_CAT, OP_SPLIT, OP_AND, OP_OR, OP_XOR, OP_DIV, OP_MOD, OP_BIN2NUM, OP_NUM2BIN
  • OP_CHECKDATASIG, OP_CHECKDATASIGVERIFY, and more malleabiliy fixes ("push only" and "clean stack" rules). This made the precedent of allowing Script to "look" at other inputs & outputs in the same transaction, which enabled first covenants.
• 2019
  • Schnorr signatures
  • Schnorr multisig, and more malleability fixes (minimal push and minimal number encoding)
• 2020
  • OP_REVERSEBYTES
• 2021
  • Allow multiple OP_RETURNs
• 2022
  • SriptVM 64-byte integer support, enabled OP_MUL
  • Native introspection opcodes: OP_INPUTINDEX, OP_ACTIVEBYTECODE, OP_TXVERSION, OP_TXINPUTCOUNT, OP_TXOUTPUTCOUNT, OP_TXLOCKTIME, OP_UTXOVALUE, OP_UTXOBYTECODE, OP_OUTPOINTTXHASH, OP_OUTPOINTINDEX, OP_INPUTBYTECODE, OP_INPUTSEQUENCENUMBER, OP_OUTPUTVALUE, OP_OUTPUTBYTECODE
• 2023
  • CashTokens - native consensus-enforced UTXO token primitives and ScriptVM opcodes (OP_UTXOTOKENCATEGORY, OP_UTXOTOKENCOMMITMENT, OP_UTXOTOKENAMOUNT, OP_OUTPUTTOKENCATEGORY, OP_OUTPUTTOKENCOMMITMENT, OP_OUTPUTTOKENAMOUNT) to integrate them with contracts
  • Address the hash collision problem by enabling a 32-byte BIP-0016 output pattern - P2SH32

Turing completeness

Bitcoin Cash Script is not Turing-complete but OP_CHECKDATASIG (2018) and introspection opcodes (2022) made transaction chains Turing-complete. There's been some work discussing why this is so: Self-Reproducing Coins as Universal Turing Machine, A. Chepurnoy, Vasily Kharin, D. Meshkov

Note that nodes wouldn't be automatically evolving the multi-TX program. Some blockchain-external agent would have to construct the next transaction that satisfies the covenant and then broadcast it to the network. The program could code-in a reward for this and incentivize anyone to construct and post the next transaction, or external agents could do it for free. The program would halt when it runs out of money for the fees/incentives, but then again, other external agents could give it more money to continue evolving.