Cargo Features

[dependencies]
ripemd = { version = "0.2.0-pre.4", default-features = false, features = ["std", "oid", "zeroize"] }
default = oid, std

These default features are set whenever ripemd is added without default-features = false somewhere in the dependency tree.

std default

Enables std of digest

oid default

Enables oid of digest

zeroize

Enables zeroize of digest

RIPEMD has 4 features without comments.