scrypt: remove incorrect N upper-bound check from Params::new#867
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tarcieri merged 1 commit intoRustCrypto:masterfrom Mar 28, 2026
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scrypt: remove incorrect N upper-bound check from Params::new#867tarcieri merged 1 commit intoRustCrypto:masterfrom
tarcieri merged 1 commit intoRustCrypto:masterfrom
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RFC 7914 specifies `N < 2^(128 * r / 8)`, i.e. `log_n < r * 16`, but this constraint contains a unit error: a bit count was treated as a byte count. The correct bound from the original scrypt paper is `N < 2^(128*r)`, which far exceeds any practical parameter value. The incorrect check rejected valid parameters such as log_n=18 with r=1 (used in Ethereum test vectors) and log_n=20 with r=1. This aligns with the Tarsnap reference implementation and Go's x/crypto/scrypt, both of which omit this check.
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## Added - Implement `PartialEq` for `scrypt::Params` (#490) - `Params::n` method (#544) - `parallel` feature using `rayon` (#733, #785) - `mcf` feature for Modular Crypt Format support (#781, #806) - SSE2/simd128 `RoMix` data layout optimization (#622) - Customizable `Params` for `Scrypt` type (#797) - Implement `kdf::{Kdf, Pbkdf}` for `Scrypt` (#823) ## Changed - Make methods of `scrypt::Params` into `const fn` (#508) - Bump edition to 2024; MSRV 1.85 (#563) - Split `Params::new` and `Params::new_with_output_len` (#602) - Use the `phc` crate for `PasswordHash` and related types (#761) - Switch from `std::error::Error` to `core::error::Error` (#767) - Rename `simple` feature to `phc` (#776) - Migrate from `subtle` to `ctutils` (#845) - Bump `password-hash` dependency to v0.6 (#848) - Bump `sha2` to v0.11 (#872) - Bump `salsa20` dependency to v0.11 (#875) - Bump `pbkdf2` dependency to v0.13 (#885) ## Removed - `Display` and `FromStr` impls for `Params` (#824) - Incorrect `N` upper-bound check from `Params::new` (#867)
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RFC 7914 specifies
N < 2^(128 * r / 8), i.e.log_n < r * 16, but this constraint contains a unit error: a bit count was treated as a byte count. The correct bound from the original scrypt paper isN < 2^(128*r), which far exceeds any practical parameter value.The incorrect check rejected valid parameters such as log_n=18 with r=1 (used in Ethereum test vectors) and log_n=20 with r=1.
This aligns with the Tarsnap reference implementation and Go's x/crypto/scrypt, both of which omit this check.
Fixes: #866
Fixes: #546
See also: https://www.rfc-editor.org/errata/eid5971