Does malleable mean modifiable?

If you can malleate a transaction you can modify some of its parts leaving the transaction as still valid (the signatures are not broken).

If you can malleate the transaction outputs you can modify the outputs.

If you can malleate the order of inputs you can modify the order of inputs.

But the bitcoin.stackexchange.com "transaction-malleability" tag says:

A property of Bitcoin transactions that allows them to be replicated with another transaction id before they are included in a block.

This confuses me. Does transaction have an ID at all, and if it does ID seems totally irrelevant?

1 Answer 1


Malleability is ability to change the binary contents of transaction (that also includes its TXID) without invalidating it, by someone else after broadcast and before the confirmation in block.

  • Couldn't the word modifiable be used instead malleable, because this is just modifying the transaction in some way, if I understand correctly?
    – croraf
    Nov 27, 2017 at 22:29
  • Hm. Let us take any txA and any txB. Can we say that txB is a modification of txA where all bytes of txA were modified to bytes of txB ? :))))
    – amaclin
    Nov 27, 2017 at 22:40
  • Than the word change (changable) instead malleate (malleable). Malleable just sounds fancy, but in fact just means change the transaction?
    – croraf
    Nov 27, 2017 at 22:42
  • 3
    It's a standard term in cryptography. Malleability specifically refers to the ability to change a signature without being authorized to sign. Nov 27, 2017 at 22:59

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