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What is Bitcoin Segregated Witness aka segwit

Mon, Feb 06, 17

Segregated Witness is a solution for the Bitcoin Core. It is spearheaded by Pieter Wuille, Johnson Lau, and Eric Lombrozo BIP141. The general idea of segwit is that the signatures in a transaction (aka witness data) are skipped when calculating the transaction id.

Segregated Witness is basically an “add-on” that carries signatures and some additional data. Importantly, Segregated Witnesses are completely ignored by old nodes, but recognized by new nodes. Moreover, the data they carry is not hashed along with the other parts of a transaction into the transaction ID.


The transaction size overhead is due to two factors:

Without these two factors, the overhead would be negligible at -3 bytes for P2WPKH and +1 bytes for P2WSH.

Segregated Witness Benefits

The Segregated Witness soft-fork (segwit) includes a wide range of features, many of which are highly technical.

Further Reading

  1. Segregated Witness Adoption
  2. Segregated Witness Costs and Risks

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