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Add advisory for timing variability in curve25519-dalek-ng #2339

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Add advisory for timing variability in curve25519-dalek-ng
fspreiss Jun 27, 2025
e17a402
Also mention PRs 662 and 665 for backports
fspreiss Jun 27, 2025
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30 changes: 30 additions & 0 deletions crates/curve25519-dalek-ng/RUSTSEC-0000-0000.md
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```toml
[advisory]
id = "RUSTSEC-0000-0000"
package = "curve25519-dalek-ng"
date = "2025-06-27"
url = "https://rustsec.org/advisories/RUSTSEC-2024-0344"
references = ["https://github.com/dalek-cryptography/curve25519-dalek/pull/659"]
categories = ["crypto-failure"]
related = ["RUSTSEC-2024-0344"]

[versions]
patched = []
```

# Timing variability of RUSTSEC-2024-0344 also applicable to `curve25519-dalek-ng`

[`curve25519-dalek-ng`](https://crates.io/crates/curve25519-dalek-ng) is a fork of [`curve25519-dalek`](https://crates.io/crates/curve25519-dalek) that was created at a time when it was still vulnerable to the timing variability reported in [RUSTSEC-2024-0344](https://rustsec.org/advisories/RUSTSEC-2024-0344).

Timing variability of any kind is problematic when working with potentially secret values such as elliptic curve scalars, and such issues can potentially leak private keys and other secrets.

To patch the vulnerability, backports of
* [curve25519-dalek/pull/659](https://github.com/dalek-cryptography/curve25519-dalek/pull/659) and [curve25519-dalek/pull/661](https://github.com/dalek-cryptography/curve25519-dalek/pull/661), or the subsequent
* [curve25519-dalek/pull/662](https://github.com/dalek-cryptography/curve25519-dalek/pull/662), or the subsequent
* [curve25519-dalek/pull/665](https://github.com/dalek-cryptography/curve25519-dalek/pull/665)

are required for `curve25519-dalek-ng`.

A patch attempt exists with [zkcrypto/curve25519-dalek-ng/pull/25](https://github.com/zkcrypto/curve25519-dalek-ng/pull/25) since Aug 14, 2024, but it remains open and unanswered. To date, there is no patched version available.

Crates that use `curve25519-dalek-ng`'s `Scalar` for private key operations are also vulnerable. An example of such a crate is [`ed25519-consensus`](https://crates.io/crates/ed25519-consensus).