Lua Requires Chilkat v11.0.0+

Create a JWS Using ECDSA P-256 SHA-256

See more JSON Web Signatures (JWS) Examples

Creates and validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256 Lua

local chilkat = require("chilkat")

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

-- Use the following ECC key loaded from JWK format.
local sbJwk = chilkat.StringBuilder.new()
sbJwk:append("{\"kty\":\"EC\",")
sbJwk:append("\"crv\":\"P-256\",")
sbJwk:append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",")
sbJwk:append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\",")
sbJwk:append("\"d\":\"jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI\"")
sbJwk:append("}")

local eccKey = chilkat.PrivateKey.new()
-- Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
-- into the private key object. (See the online reference documentation..)
local success = eccKey:load_jwk(sbJwk:get_as_string())
if not success then
    print(eccKey.last_error_text)
    return
end

-- Create the JWS Protected Header
local jwsProtHdr = chilkat.JsonObject.new()
jwsProtHdr:append_string("alg", "ES256")

local jws = chilkat.Jws.new()

-- Set the protected header:
local signatureIndex = 0
jws:set_protected_header(signatureIndex, jwsProtHdr)

-- Set the ECC key:
jws:set_private_key(signatureIndex, eccKey)

-- Set the payload.
local bIncludeBom = false
local payloadStr = "In our village, folks say God crumbles up the old moon into stars."
jws:set_payload(payloadStr, "utf-8", bIncludeBom)

-- Create the JWS
-- By default, the compact serialization is used.
local jwsCompact = jws:create_jws()
if not jws.last_method_success then
    print(jws.last_error_text)
    return
end

print("JWS: " .. jwsCompact)

-- Note: ECC signatures use random values, so the output will be different each time a signature is produced.
-- sample output:
-- JWS: eyJhbGciOiJFUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.J6EGTNkeuEjehHHBu0SOKzifm8r35wbx49A5964pxzB7gannyZZPMkK7vmlaPJ-K8Xmm8cZsQySAPC12Xd8avw

-- Now load the JWS, validate, and recover the original text.
local jws2 = chilkat.Jws.new()

-- Load the JWS.
success = jws2:load_jws(jwsCompact)

local eccPubKey = chilkat.PublicKey.new()
eccKey:to_public_key(eccPubKey)

-- Set the ECC public key used for validation.
signatureIndex = 0
jws2:set_public_key(signatureIndex, eccPubKey)

-- Validate the 1st (and only) signature at index 0..
local v = jws2:validate(signatureIndex)
if v < 0 then
    -- Perhaps Chilkat was not unlocked or the trial expired..
    print("Method call failed for some other reason.")
    print(jws2.last_error_text)
    return
end

if v == 0 then
    print("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.")
    return
end

-- If we get here, the signature was validated..
print("Signature validated.")

-- Recover the original content:
print(jws2:get_payload("utf-8"))

-- Examine the protected header:
local joseHeader = chilkat.JsonObject.new()
jws2:get_protected_h(signatureIndex, joseHeader)
joseHeader.emit_compact = false

print("Protected (JOSE) header:")
print(joseHeader:emit())

-- Output:

-- Signature validated.
-- In our village, folks say God crumbles up the old moon into stars.
-- Protected (JOSE) header:
-- {
--   "alg": "ES256"
-- }