Lua Requires Chilkat v11.0.0+

Verify an RSA Signature Against the Signed String

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the string that was signed. Lua

local chilkat = require("chilkat")

-- Create the same string we previously signed in this example:
-- RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

local sb = chilkat.StringBuilder.new()
local crlfLineEnding = true
for i = 0, 10 do
    sb:append_line("This is a test.", crlfLineEnding)
end

local base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ=="

-- Get the public key to be used for signature verification.
local pubKey = chilkat.PublicKey.new()
local success = pubKey:load_from_file("rsaKeys/chilkat-rsa-2048.pem")
if not success then
    print(pubKey.last_error_text)
    return
end

local rsa = chilkat.Rsa.new()
success = rsa:use_public_key(pubKey)
if not success then
    print(rsa.last_error_text)
    return
end

-- Verify the string against the signature.
-- We signed the utf-8 byte representation of the string, so we must indicate
-- to also validate against the utf-8 byte representation.
rsa.charset = "utf-8"
rsa.encoding_mode = "base64"
local signedString = sb:get_as_string()
success = rsa:verify_string_enc(signedString, "sha256", base64_rsa_sig)

if not success then
    print(rsa.last_error_text)
    print("Signature invalid.")
else
    print("Signature valid.")
end