Prerequisites:

• python3 (for: build, test)
• gcc and/or clang (for: build)
• valgrind (for: build, test)
• libcpucycles (for: build, bench)
• librandombytes (for: build, test, bench, run)

Make sure to test the compiled library. The tests check for subtle security problems that can be created by compilers. A compiled version of lib25519 is not supported unless it passes the full test suite.

For sysadmins

To install in /usr/local/{include,lib,bin,man}:

./configure && make -j8 install

For developers with an unprivileged account

Typically you'll already have

export LD_LIBRARY_PATH="$HOME/lib"
export LIBRARY_PATH="$HOME/lib"
export CPATH="$HOME/include"
export MANPATH="$HOME/man"
export PATH="$HOME/bin:$PATH"

in $HOME/.profile. To install in $HOME/{include,lib,bin,man}:

./configure --prefix=$HOME && make -j8 install

For distributors creating a package

Run

./configure --prefix=/usr && make -j8

and then follow your usual packaging procedures for the build/0/package files:

build/0/package/include/lib25519.h
build/0/package/lib/lib25519*
build/0/package/bin/lib25519*
build/0/package/man/man3/*.3
build/0/package/man/man1/*.1

More options, part 1: s2n-bignum

Before ./configure you can run ./use-s2n-bignum to download various .S files from s2n-bignum and integrate them into lib25519. The critical feature of these .S files is that they are formally verified to work correctly on all inputs. The files cover, for 64-bit Intel/AMD/ARM, the main nG and nP subroutines used in X25519 key generation and shared-secret generation; the files also save some time on some of these CPUs, although not all. If you want to disable the other nG and nP implementations, you can run chmod +t crypto_{nP,nG}/montgomery25519/* before running ./use-s2n-bignum.

More options, part 2: architectures

You can run

./configure --host=amd64

to override ./configure's guess of the architecture that it should compile for.

Inside the build directory, 0 is symlinked to amd64 for --host=amd64. Running make clean removes build/amd64. Re-running ./configure automatically starts with make clean.

A subsequent ./configure --host=arm64 will create build/arm64 and symlink 0 -> arm64, without touching an existing build/amd64. However, cross-compilers aren't yet selected automatically.

More options, part 3

One further ./configure option is supported for developers: --no-trim.

All ./configure options not listed above are experimental and not supported. Use them at your own risk.

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Version: This is version 2024.09.25 of the "Install" web page.