official implementations of the BLAKE3 cryptographic hash function
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Jack O'Connor 35aa4259bd version 0.3.7 1 month ago
src put the file name in b3sum error output 5 months ago
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Cargo.toml version 0.3.7 1 month ago use an absolute url for 2 months ago fix a typo in the docs 6 months ago


A command line utility for calculating BLAKE3 hashes, similar to Coreutils tools like b2sum or md5sum.

b3sum 0.3.6

    b3sum [FLAGS] [OPTIONS] [FILE]...

    -c, --check       Reads BLAKE3 sums from the [file]s and checks them
    -h, --help        Prints help information
        --keyed       Uses the keyed mode. The secret key is read from standard
                      input, and it must be exactly 32 raw bytes.
        --no-mmap     Disables memory mapping. Currently this also disables
        --no-names    Omits filenames in the output
        --quiet       Skips printing OK for each successfully verified file.
                      Must be used with --check.
        --raw         Writes raw output bytes to stdout, rather than hex.
                      --no-names is implied. In this case, only a single
                      input is allowed.
    -V, --version     Prints version information

        --derive-key <CONTEXT>    Uses the key derivation mode, with the given
                                  context string. Cannot be used with --keyed.
    -l, --length <LEN>            The number of output bytes, prior to hex
                                  encoding (default 32)
        --num-threads <NUM>       The maximum number of threads to use. By
                                  default, this is the number of logical cores.
                                  If this flag is omitted, or if its value is 0,
                                  RAYON_NUM_THREADS is also respected.

    <FILE>...    Files to hash, or checkfiles to check. When no file is given,
                 or when - is given, read standard input.

See also this document about how the --check flag works.


Hash the file foo.txt:

b3sum foo.txt

Time hashing a gigabyte of data, to see how fast it is:

# Create a 1 GB file.
head -c 1000000000 /dev/zero > /tmp/bigfile
# Hash it with SHA-256.
time openssl sha256 /tmp/bigfile
# Hash it with BLAKE3.
time b3sum /tmp/bigfile


Prebuilt binaries are available for Linux, Windows, and macOS (requiring the unidentified developer workaround) on the releases page. If you've installed Rust and Cargo, you can also build b3sum yourself with:

cargo install b3sum

On Linux for example, Cargo will put the compiled binary in ~/.cargo/bin. You might want to add that directory to your $PATH, or rustup might have done it for you when you installed Cargo.

If you want to install directly from this directory, you can run cargo install --path .. Or you can just build with cargo build --release, which puts the binary at ./target/release/b3sum.