ECDSA Util

Requirements

• libuecc: http://git.universe-factory.net/libuecc

Building

mkdir build
cd build
cmake ..
make

Binary will be in build/src.

Utilities

generate-key

The secret is written to stdout.

% ecdsautil generate-key > secret
% cat secret
68b12c0eaf88bf17fbcdf560780136b9cc4be352fb8aa7148215fbd65887db7b

show-key

The secret should be supplied on stdin. The public key will be written to stdout.

% ecdsautil show-key < secret
1f63ef7450760af9062ff697995eb536eef25a555822087fa4cfd9a82d9faa79

sign

If you have followed the previous examples you should have a file called secret containing the private key. Using a secret you can sign a file like this:

% ecdsautil sign somefile < secret
da967af925168d8eb113bc79a60717b444d24c0dab449a90b1360dc849d1150fc6fe5e6656966d2fc88e67d81108deb13836ed66308cf897dd1b8815f6422802

verify

ecdsautil verify is quite powerful utility for verification of signatures. You can verify a simple signature like this:

% ecdsautil verify -s da967...802 -p 1f63ef7450760af9062ff697995eb536eef25a555822087fa4cfd9a82d9faa79 somefile
% echo $?
0

Usually, there is no output except the return code. A return code of 0 denotes a correct signature. If the signature is invalid, 1 is returned.

n-of-m verification

Multiple signatures and public keys may be supplied to facilitate n-of-m verifications:

% ecdsautil verify -s signature1 -s signature2 ... -p pubkey1 -p pubkey2 ... somefile

In this mode it is checked whether any supplied public key can be used to verify any supplied signature. This can be used in cases where multiple parties (each with their own private key) are allowed to sign a file. This is called 1-of-m verification.

This can further be expanded into n-of-m verification using the -n switch:

% ecdsautil verify -s sig1 -s sig2 -s sig3 -p pub1 -p pub2 -p pub3 -p pub4 -n 2

In this case at least two pairs of public key and signature must match.

Signature Format

concat $ map tohexstring [r, s]

libecdsautil

ecdsautil can easily be embedded into other applications. A pkg-config file called ecdsautil.pc is provided for easy compiling and linking against libecdsautil.

For API documentation see the public header file <ecdsautil/ecdsa.h> (and <ecdsautil/sha256.h> for the included SHA256 implementation). If you have installed Doxygen, make doxygen can be used to generated HTML documentation of libecdsautil.

libecdsautil does not provide functions for the generate-key and show-key commands, as these are already provided by libuecc (see ecc_25519_gf_sanitize_secret and ecc_25519_scalarmult_base).

Release precedure

• update debian/changelog
• create debian package
• update AUR package