From an example in the documentation:

$ bx seed | bx mnemonic-new | bx mnemonic-to-seed | bx hd-new

655a1ed2d4fef69bb314198c7327f23c grab special regret prepare urge evidence slush lobster midnight odor wish ketchup 57bae342ae8e69eb63f17ef993a90a59159e0f78114b602bf0ebabfec0e5d086e883c31975bf03f8a47a32853452623094d1303fd0549745db457145e5756582 xprv9s21ZrQH143K43CUCgNp5SmXzg2axQx2P4WupA2zEnKpFM19QfqfdqfpJR3yfzAXZnsHeUaQhWQMwyuqL8DbdeLeCbdMoKNn6pCY4RUn2pK

In Mastering Bitcoin, the example given here shows it going back to the seed that was originally created; this was done using an older version of bx though. Can someone explain how the seeds from line 1 and line 3 in the example are encoded/related?

3 Answers 3


They adopted bip39 where the seed mnemonic is run through a key derivation function to derive the seed. This is an irreversible step.

  • answering the wrong question, overloading the term "seed" is too common
    – HansBKK
    Feb 20, 2022 at 4:17

Fundamental flaw here, multiple meanings of the word "seed"even within discussion of just BIP39.

The "entropy" is a better term for the BIP39 starting point. Then the endpoint of the process should be "BIP39 numeric seed".

"Convert the entropy to a BIP39 mnemonic. Use that mnemonic plus a (technically optional but no) passphrase as the inputs to produce the BIP39 numeric seed. End of BIP39. "

is how I would tell the story.

Now, looking at this from *Mastering Bitcoin *

The seed can be encoded using the mnemonic-encode command:

$ bx hd-mnemonic < seed > words adore repeat vision worst especially veil inch woman cast recall dwell appreciate

The seed can then be decoded using the mnemonic-decode command:

$ bx mnemonic-decode < words eb68ee9f3df6bd4441a9feadec179ff1

Andreas Antonopoulos is here clearly using "seed" to refer to the entropy. The process described does not involve hashing, or cryptographic "encoding", it's just a change in representation, like going from binary to hex.

Except for the N/32 checksum getting added.

Which means an input entropy of 256 bits is entirely reversible, but the last 8 bits to get to 264 (24 words x 11 bits) is the result of the checksum process.

What the other answers here are referring to is not the "entropy seed" but the output, the "BIP39 numeric seed" which is indeed a one way derivation process.

I believe the bx mnemonic-decode command may have gotten removed simply because it is useless, or at least I cannot think of a use case.

I do not think it stopped working in the transition to BIP39. EDIT The entropy to mnemonic "conversion" is reversed by many tools - see https://iancoleman.app


I asked the same questions regarding the example in Mastering Bitcoin and here is the answer:

The old mnemonic-decode (electrum v1 mnemonics I believe) was dropped from libbitcoin before version3 and replaced with BIP-39 mnemonics. libbitcoin version4 also adds in electrum v2 mnemonics. Unlike electrum v1 mnemonics (which are symmetric), BIP-39 is asymmetric --https://github.com/libbitcoin/libbitcoin-explorer/issues/366

  • asking the wrong question, overloading the term "seed" is too common
    – HansBKK
    Feb 20, 2022 at 4:16

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