The ristretto255 Group

Document Type Replaced Internet-Draft (cfrg RG)
Authors Henry de Valence  , Jack Grigg  , George Tankersley  , Filippo Valsorda  , Isis Lovecruft 
Last updated 2020-08-04 (latest revision 2020-05-04)
Replaces draft-hdevalence-cfrg-ristretto
Replaced by draft-irtf-cfrg-ristretto255-decaf448
Stream Internet Research Task Force (IRTF)
Intended RFC status Informational
Expired & archived
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Stream IRTF state Replaced
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IESG IESG state Replaced by draft-irtf-cfrg-ristretto255-decaf448
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This memo specifies a prime-order group, ristretto255, suitable for safely implementing higher-level and complex cryptographic protocols. The ristretto255 group can be implemented using Curve25519, allowing existing Curve25519 implementations to be reused and extended to provide a prime-order group.


Henry de Valence (
Jack Grigg (
George Tankersley (
Filippo Valsorda (
Isis Lovecruft (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)