* [bitcoindev] Allowing Duplicate Keys in BIP 390 musig() Expressions @ 2025-06-03 21:07 'Ava Chow' via Bitcoin Development Mailing List 2025-06-03 21:26 ` Nagaev Boris 0 siblings, 1 reply; 3+ messages in thread From: 'Ava Chow' via Bitcoin Development Mailing List @ 2025-06-03 21:07 UTC (permalink / raw) To: bitcoindev Hi All, In implementing musig() descriptor expressions, I realized that the restriction "Repeated participant public keys are not allowed" is a bit complicated to implement. While I don't see why anyone would want to duplicate keys, MuSig2 does allow duplicate participant keys and allowing them would make the implementation of musig() expressions much easier. Thus I'd like to propose changing the BIP to remove this restriction. Has anyone implemented musig() expressions yet with this restriction, and would removing it be a significant breaking change to anyone? If not, I'll make the change to the BIP in a few days. Thanks, Ava -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/08dbeffd-64ec-4ade-b297-6d2cbeb5401c%40achow101.com. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [bitcoindev] Allowing Duplicate Keys in BIP 390 musig() Expressions 2025-06-03 21:07 [bitcoindev] Allowing Duplicate Keys in BIP 390 musig() Expressions 'Ava Chow' via Bitcoin Development Mailing List @ 2025-06-03 21:26 ` Nagaev Boris 2025-06-03 21:38 ` 'Ava Chow' via Bitcoin Development Mailing List 0 siblings, 1 reply; 3+ messages in thread From: Nagaev Boris @ 2025-06-03 21:26 UTC (permalink / raw) To: Ava Chow; +Cc: bitcoindev Hi Ava, Is it safe to allow multiple participants to have the same public key? If deterministic nonce generation is used (deriving each participant's nonce from the message, the set of public keys, and the participant's private key), duplicate public keys would lead to identical nonces. While this may not be catastrophic (since they are signing the same message and the private key likely can't be extracted) it still seems risky. Identical nonces can have unexpected consequences, and I'm not sure if all security assumptions would still hold. Curious what you think. Best, Boris On Tue, Jun 3, 2025 at 6:08 PM 'Ava Chow' via Bitcoin Development Mailing List <bitcoindev@googlegroups.com> wrote: > > Hi All, > > In implementing musig() descriptor expressions, I realized that the > restriction "Repeated participant public keys are not allowed" is a bit > complicated to implement. While I don't see why anyone would want to > duplicate keys, MuSig2 does allow duplicate participant keys and > allowing them would make the implementation of musig() expressions much > easier. Thus I'd like to propose changing the BIP to remove this > restriction. > > Has anyone implemented musig() expressions yet with this restriction, > and would removing it be a significant breaking change to anyone? If > not, I'll make the change to the BIP in a few days. > > Thanks, > > Ava > > > -- > You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. > To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com. > To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/08dbeffd-64ec-4ade-b297-6d2cbeb5401c%40achow101.com. -- Best regards, Boris Nagaev -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/CAFC_Vt5z%2BB%2BF%3DQOytZ96ptRFweX1aGBV-CXHqwv54UAyo_iiAw%40mail.gmail.com. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [bitcoindev] Allowing Duplicate Keys in BIP 390 musig() Expressions 2025-06-03 21:26 ` Nagaev Boris @ 2025-06-03 21:38 ` 'Ava Chow' via Bitcoin Development Mailing List 0 siblings, 0 replies; 3+ messages in thread From: 'Ava Chow' via Bitcoin Development Mailing List @ 2025-06-03 21:38 UTC (permalink / raw) To: Nagaev Boris; +Cc: bitcoindev Hi Boris, BIP 327 explicitly allows for duplicate participant pubkeys, so as long as all signing procedures follow the BIP, everything will be fine. Also, BIP 327 explicitly warns against deterministic nonces for reasons unrelated to duplicate pubkeys. Although, allowing duplicates does bring up an additional issue with the MuSig2 PSBT fields as these inherently do not allow duplicate pubkeys. Ava On 06/03/2025 02:26 PM, Nagaev Boris wrote: > Hi Ava, > > Is it safe to allow multiple participants to have the same public key? > If deterministic nonce generation is used (deriving each participant's > nonce from the message, the set of public keys, and the participant's > private key), duplicate public keys would lead to identical nonces. > > While this may not be catastrophic (since they are signing the same > message and the private key likely can't be extracted) it still seems > risky. Identical nonces can have unexpected consequences, and I'm not > sure if all security assumptions would still hold. > > Curious what you think. > > Best, > Boris > > On Tue, Jun 3, 2025 at 6:08 PM 'Ava Chow' via Bitcoin Development > Mailing List <bitcoindev@googlegroups.com> wrote: >> Hi All, >> >> In implementing musig() descriptor expressions, I realized that the >> restriction "Repeated participant public keys are not allowed" is a bit >> complicated to implement. While I don't see why anyone would want to >> duplicate keys, MuSig2 does allow duplicate participant keys and >> allowing them would make the implementation of musig() expressions much >> easier. Thus I'd like to propose changing the BIP to remove this >> restriction. >> >> Has anyone implemented musig() expressions yet with this restriction, >> and would removing it be a significant breaking change to anyone? If >> not, I'll make the change to the BIP in a few days. >> >> Thanks, >> >> Ava >> >> >> -- >> You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. >> To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com. >> To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/08dbeffd-64ec-4ade-b297-6d2cbeb5401c%40achow101.com. > > > -- > Best regards, > Boris Nagaev -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/9a25e808-1821-404c-bd47-f0ab78bca936%40achow101.com. ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2025-06-03 21:40 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2025-06-03 21:07 [bitcoindev] Allowing Duplicate Keys in BIP 390 musig() Expressions 'Ava Chow' via Bitcoin Development Mailing List 2025-06-03 21:26 ` Nagaev Boris 2025-06-03 21:38 ` 'Ava Chow' via Bitcoin Development Mailing List
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