CIRCL
CIRCL (Cloudflare Interoperable, Reusable Cryptographic Library) is a collection
of cryptographic primitives written in Go. The goal of this library is to be used as a tool for
experimental deployment of cryptographic algorithms targeting Post-Quantum (PQ) and Elliptic
Curve Cryptography (ECC).
Security Disclaimer
🚨 This library is offered as-is, and without a guarantee. Therefore, it is expected that changes in the code, repository, and API occur in the future. We recommend to take caution before using this library in a production application since part of its content is experimental. All security issues must be reported, please notify us immediately following the instructions given in our Security Policy.
Constant-Time Caveats
⚠️ Not every package in CIRCL is constant time. The following packages document, at the
top of their doc.go or main source file, the specific operations that are known to
leak timing information: group/, oprf/,
blindsign/blindrsa/partiallyblindrsa/,
secretsharing/, tss/rsa/, zk/dl/,
zk/dleq/, and ecc/p384/.
Installation
You can get CIRCL by fetching:
go get -u github.com/cloudflare/circl
Alternatively, look at the Cloudflare Go fork to see how to integrate CIRCL natively in Go.
List of Algorithms
Elliptic Curve Cryptography
| Digital Signature Schemes |
Post-Quantum Cryptography
| KEM: Key Encapsulation Methods |
| Digital Signature Schemes |
Zero-knowledge Proofs
- Schnorr: Prove knowledge of the Discrete Logarithm. (RFC-8235)
- DLEQ: Prove knowledge of the Discrete Logarithm Equality. (RFC-9497)
- DLEQ in Qn: Prove knowledge of the Discrete Logarithm Equality for subgroup of squares in (Z/nZ)*.
Symmetric Cryptography
| XOF: eXtendable Output Functions |
| LWC: Lightweight Cryptography |
Misc
- Safe primes generation.
- Integer encoding: wNAF, regular signed digit, mLSBSet representations.
- Fp25519, Fp448, Fp511, Fp434, Fp503, Fp751.
- Fp381, and its quadratic, sextic and twelveth extensions.
- Polynomials in monomial and Lagrange basis.
Testing and Benchmarking
Library comes with number of make targets which can be used for testing and
benchmarking:
test performs testing of the binary.bench runs benchmarks.cover produces coverage.lint runs set of linters on the code base.
Contributing
To contribute, fork this repository and make your changes, and then make a Pull
Request. A Pull Request requires approval of the admin team and a successful
CI build.
How to Cite
To cite CIRCL, use one of the following formats and update the version and date you accessed this project.
APA Style
Faz-Hernandez, A. and Kwiatkowski, K. (2019). Introducing CIRCL:
An Advanced Cryptographic Library. Cloudflare. Available at
https://github.com/cloudflare/circl. v1.6.4 Accessed Jun, 2026.
BibTeX Source
@manual{circl,
title = {Introducing CIRCL: An Advanced Cryptographic Library},
author = {Armando Faz-Hernandez and Kris Kwiatkowski},
organization = {Cloudflare},
abstract = {{CIRCL (Cloudflare Interoperable, Reusable Cryptographic Library) is
a collection of cryptographic primitives written in Go. The goal
of this library is to be used as a tool for experimental
deployment of cryptographic algorithms targeting Post-Quantum (PQ)
and Elliptic Curve Cryptography (ECC).}},
note = {Available at \url{https://github.com/cloudflare/circl}. v1.6.4 Accessed Jun, 2026},
month = jun,
year = {2019}
}
CFF Style
See attached CITATION.cff file.
License
The project is licensed under the BSD-3-Clause License.
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