Why is there a tag and obsoleteTag in a transaction? In the code, I could find one usage (iota.lib.js) of the obsoleteTag being incremented if the normalized hash is considered insecure. This implies that one can't be sure that the obsoleteTag, or a small part of it, changes during bundle creation.

1 Answer 1


obsoleteTag will be removed soon. The preliminary final design of the bundle essence fragment is:

extraDataDigest [243 trits]

address [243 trits]

value [81 trits]

issuanceTimestamp [27 trits]

timelockLowerBound [27 trits]

timelockUpperBound [27 trits]

bundleNonce [81 trits]

Now that part contains obsoleteTag.

  • Is there any documentation which covers these changes?
    – Daniel F
    Jan 13, 2018 at 12:54
  • No documentation, the changes haven't been tested yet. Jan 13, 2018 at 13:02
  • What is the bundleNonce? POW nonce? Jan 13, 2018 at 14:26
  • No, PoW nonce is in another place of the transactions. bundleNonce replaces Winternitz checksum. Jan 13, 2018 at 15:52
  • @Come-from-Beyond Is there a reference or document with the final design?
    – mike
    Mar 16, 2019 at 22:57

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