Lua

ECDSA Sign Data and Verify Signature

See more ECC Examples

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature. Lua

local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

-- To create an ECDSA signature, the data first needs to be hashed.  Then the hash
-- is signed.

-- Use Chilkat Crypt2 to generate a hash for any of the following
-- hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

local crypt = chilkat.Crypt2.new()
crypt.hash_algorithm = "SHA256"
crypt.charset = "utf-8"
crypt.encoding_mode = "base64"

-- Hash a string.
local hash1 = crypt:hash_string_enc("The quick brown fox jumps over the lazy dog")
print("hash1 = " .. hash1)

-- Or hash a file..
local hash2 = crypt:hash_file_enc("qa_data/hamlet.xml")
print("hash2 = " .. hash2)

-- (The Crypt2 API provides many other ways to hash data..)

-- -----------------------------------------------------------
-- An ECDSA private key is used for signing.  The public key is for signature verification.
-- Load our ECC private key.
-- Our private key file contains this:

--     // -----BEGIN PRIVATE KEY-----
--     MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
--     72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
--     a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
--     -----END PRIVATE KEY-----

local privKey = chilkat.PrivateKey.new()
local success = privKey:load_pem_file("qa_data/ecc/secp256r1-key-pkcs8.pem")
if not success then
    print(privKey.last_error_text)
    return
end

-- We'll need a PRNG source for random number generation.
-- Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
local prng = chilkat.Prng.new()

-- Sign the hash..
local ecdsa = chilkat.Ecc.new()
local ecdsaSigBase64 = ecdsa:sign_hash_enc(hash1, "base64", privKey, prng)
if not ecdsa.last_method_success then
    print(ecdsa.last_error_text)
    return
end

print("ECDSA signature = " .. ecdsaSigBase64)

-- -----------------------------------------------------------
-- Now let's verify the signature using the public key.

local pubKey = chilkat.PublicKey.new()
success = pubKey:load_from_file("qa_data/ecc/secp256r1-pubkey.pem")
if not success then
    print(pubKey.last_error_text)
    return
end

local result = ecdsa:verify_hash_enc(hash1, ecdsaSigBase64, "base64", pubKey)
if result == 1 then
    print("Signature is valid.")
    return
end

if result == 0 then
    print("Signature is invalid.")
    return
end

if result < 0 then
    print(ecdsa.last_error_text)
    print("The VerifyHashENC method call failed.")
    return
end