The anatomy of a Nut
Cashu open source contributor
2025, Chiang Mai
What is a nut?
Can we genetically engineer nuts?
How are nuts made?
Show me your nuts
Topics
What is a nut?
Nut == Token == Proofs == Ecash
A nut (ecash token) is a proof
that a secret has been previously blindly signed with a given key
+
=
How are nuts made?
Secret
Blinding factor
Fertilizer (AKA mint signature)
Nut anatomy 101
Secret
Signature
KeysetID
Amount
{ "secret":"1ea6f7f0e907f5841285a3815a74c84e6d710b0b458b959d68c9d60aabbb40ac", "C":"02c6ee49eabc2bb027973ab5c79cdf379a74fff0731ccbae3b0d419b3d635075e6", "amount":1, "id":"00b4cd27d8861a44" }
Can we genetically engineer nuts?
Nut anatomy: Recovarable
{ "secret":"1ea6f7f0e907f5841285a3815a74c84e6d710b0b458b959d68c9d60aabbb40ac", "C":"02c6ee49eabc2bb027973ab5c79cdf379a74fff0731ccbae3b0d419b3d635075e6", "amount":1, "id":"00b4cd27d8861a44" }
{ "deterministic_secret":"1ea6f7f0e907f5841285a3815a74c84e6d710b0b458b959d68c9d60aabbb40ac", "deterministic_blinding_factor":"02c6ee49eabc2bb027973ab5c79cdf379a74fff0731ccbae3b0d419b3d635075e6", }
Nut anatomy: Well known secret / script
{ "amount": 1, "secret": "[\"P2PK\",{\"nonce\":\"859d4935c4907062a6297cf4e663e2835d90d97ecdd510745d32f6816323a41f\",\"data\":\"0249098aa8b9d2fbec49ff8598feb17b592b986e62319a4fa488a3dc36387157a7\",\"tags\":[[\"sigflag\",\"SIG_INPUTS\"]]}]", "C": "02698c4e2b5f9534cd0687d87513c759790cf829aa5739184a3e3735471fbda904", "id": "009a1f293253e41e", "witness": "{\"signatures\":[\"60f3c9b766770b46caac1d27e1ae6b77c8866ebaeba0b9489fe6a15a837eaa6fcd6eaa825499c72ac342983983fd3ba3a8a41f56677cc99ffd73da68b59e1383\"]}" }
Ex: P2PK lock
Nut anatomy: HTLC
[ "HTLC", { "nonce": "da62796403af76c80cd6ce9153ed3746", "data": "023192200a0cfd3867e48eb63b03ff599c7e46c8f4e41146b2d281173ca6c50c54", "tags": [ [ "pubkeys", "02698c4e2b5f9534cd0687d87513c759790cf829aa5739184a3e3735471fbda904" ], ["locktime", "1689418329"], [ "refund", "033281c37677ea273eb7183b783067f5244933ef78d8c3f15b1a77cb246099c26e" ] ] } ]
Ex: P2PK lock
Nut anatomy: Offline verify
{ "id": <str>, "amount": <int>, "secret": <str>, "C": <str>, "dleq": { <- "e": <str>, "s": <str>, "r": <str> } }
With DLEQ proof
Proof that blind signature was from mint's key
Nut anatomy: Offline receivable
P2PK + DLEQ = Offline receivable
{ "amount": 1, "secret": "[\"P2PK\",{\"nonce\":\"859d4935c4907062a6297cf4e663e2835d90d97ecdd510745d32f6816323a41f\",\"data\":\"0249098aa8b9d2fbec49ff8598feb17b592b986e62319a4fa488a3dc36387157a7\",\"tags\":[[\"sigflag\",\"SIG_INPUTS\"]]}]", "C": "02698c4e2b5f9534cd0687d87513c759790cf829aa5739184a3e3735471fbda904", "id": "009a1f293253e41e", "witness": "{\"signatures\":[\"60f3c9b766770b46caac1d27e1ae6b77c8866ebaeba0b9489fe6a15a837eaa6fcd6eaa825499c72ac342983983fd3ba3a8a41f56677cc99ffd73da68b59e1383\"]}" "dleq": { "e": "<str>", "s": "<str>", "r": "<str>" } }
Nut anatomy: Fully offline transaction
P2PK + timelock + refund + DLEQ = Offline transaction
{ "amount": 1, "secret": [ "P2PK", { "nonce": "da62796403af76c80cd6ce9153ed3746", "data": "033281c37677ea273eb7183b783067f5244933ef78d8c3f15b1a77cb246099c26e", "tags": [ ["locktime", "1689418329"], [ "refund", "033281c37677ea273eb7183b783067f5244933ef78d8c3f15b1a77cb246099c26e" ], [ "pubkeys", "023192200a0cfd3867e48eb63b03ff599c7e46c8f4e41146b2d281173ca6c50c54" ] ] } ], "C": "02698c4e2b5f9534cd0687d87513c759790cf829aa5739184a3e3735471fbda904", "id": "009a1f293253e41e", "witness": { "signatures": "<Array[<hex_str>]>" }, "dleq": { ... } }
Nut anatomy: Fully offline transaction
Online
Alice
Bob
Mint
Get pubkey
Mint locked ecash
Send ecash
Offline (QR)
Verify offline
- Pubkey lock
- unique secret
- Refund timelock (buffer)
- dleq
Redeem before refund timelock expires
Thank you!
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