How or in which format should Schnorr signature keys be stored?

Razvan Marian

11/30/22, 8:54 AM

I would like to know if there is any standard for storing public and private keys for Schnorr signature

1 + 1

schnorr-signature

pki

fgrieu

11/30/22, 10:28 AM

There are many variants of Schnorr signatures, on different kinds of groups; see e.g. [this](https://crypto.stackexchange.com/q/34863/555). Does the context specify something, like the group used?

Score:1

Crypto

DannyNiu

11/30/22, 10:27 AM

There is none. Schnorr's signature had only ever been academically described, so ~~no standard for it~~ there is all variaty of potentially incompatible specifications for it, lacking a uniform standard. There was standard for ElGamel encryption when NIST was running the OSI Implementor's Workshop, but it wasn't widely used.

There is however, EdDSA, which is a composition of Edwards elliptic curve with Schnorr's signature. It's specified in RFC-8032.

Of course, lacking a uniform standard doesn't prevent us from storing private key as big-endian integers and public keys as big-endian integers or elliptic curve points. All you need is to choose an existing standard (e.g. PKCS#3, SEC#1, IEEE-1363, ISO/IEC-14888-3, etc.) and apply its encoding to the academic version of Schnorr.

0 + 4

fgrieu

11/30/22, 10:49 AM

Can't agree with "no standard for it". There are too many! For example; [ISO/IEC 14888-3](https://www.iso.org/obp/ui/en/#!iso:std:76382:en) standardizes "Elliptic Curve Schnorr Digital Signature Algorithm" as EC-SDSA \[OID [1.0.14888.3.0.11](http://oid-info.com/get/1.0.14888.3.0.11)\] with variant EC-SDSA-opt \[OID [1.0.14888.3.0.13](http://oid-info.com/get/1.0.14888.3.0.13)\], and EC-FSDSA \[OID [1.0.14888.3.0.12](http://oid-info.com/get/1.0.14888.3.0.12)\]. EC-SDSA-opt is endorsed by ETSI, and BSI also an ECSDSA (with a fix). I was told one of these is used in a Smart Card application.

DannyNiu

11/30/22, 12:36 PM

@fgrieu Is my new wording acceptable?

Razvan Marian

11/30/22, 1:39 PM

Ok, but i would like to know if there is any known way to save and store the Schnorr keys like you would do with ECDSA's or RSA's

DannyNiu

11/30/22, 2:17 PM

@RazvanMarian Added a paragraph for you.

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EN: How or in which format should Schnorr signature keys be stored?

TH: How or in which format should Schnorr signature keys be stored?

RO: How or in which format should Schnorr signature keys be stored?

RU: How or in which format should Schnorr signature keys be stored?

VI: How or in which format should Schnorr signature keys be stored?

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