Lua Requires Chilkat v9.5.0.66+

JWE Using Flattened JWE JSON Serialization

See more JSON Web Encryption (JWE) Examples

This example duplicates the example A.5 in RFC 7516 for JSON Web Encryption (JWE).

This example demonstrates using the flattened JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the plaintext to a single recipient in a flattened JSON structure.

Lua

local chilkat = require("chilkat")

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

local plaintext = "Live long and prosper."

local jwe = chilkat.Jwe.new()

-- First build the JWE Protected Header: {"enc":"A128CBC-HS256"}
local jweProtHdr = chilkat.JsonObject.new()
jweProtHdr:append_string("enc", "A128CBC-HS256")
jwe:set_protected_header(jweProtHdr)

-- We have a single recipient that uses AES Key Wrap to encrypt the CEK.
--
--      {"alg":"A128KW","kid":"7"}

local jweRecipientHdr = chilkat.JsonObject.new()
jweRecipientHdr:append_string("alg", "A128KW")
jweRecipientHdr:append_string("kid", "7")
local recipientIndex = 0
jwe:set_recipient_header(recipientIndex, jweRecipientHdr)

-- Set the Shared Unprotected Header:  {"jku":"https://server.example.com/keys.jwks"}
local jweUnprotHdr = chilkat.JsonObject.new()
jweUnprotHdr:append_string("jku", "https://server.example.com/keys.jwks")
jwe:set_unprotected_header(jweUnprotHdr)

-- Set the AES key wrapping key.
local aesWrappingKey = "GawgguFyGrWKav7AX4VKUg"
recipientIndex = 0
jwe:set_wrapping_key(recipientIndex, aesWrappingKey, "base64url")

-- OK.. everything has been specified.
-- Now encrypt.
-- Indicate that we prefer the flattened JSON serialization.
jwe.prefer_flattened = true
local strJwe = jwe:encrypt(plaintext, "utf-8")
if not jwe.last_method_success then
    print(jwe.last_error_text)
    return
end

-- The JWE is produced in the most compact form possible (a single line).
-- Let's load it into a JSON object and examine in a non-compact pretty-printed format:
local jsonTemp = chilkat.JsonObject.new()
jsonTemp:load(strJwe)
jsonTemp.emit_compact = false
print(jsonTemp:emit())

-- The JWE looks like this:
-- (Note: Because of random values used in the encryption process, your encrypted results will be different.)

--     {
--       "protected": "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
--       "unprotected": {
--         "jku": "https://server.example.com/keys.jwks"
--       },
--       "header": {
--         "alg": "A128KW",
--         "kid": "7"
--       },
--       "encrypted_key": "FW7z9VxOvnF2ClicvUT4HTeqcdyh90C6qytfEFJsOb77FOwTfYrc3w",
--       "iv": "O6Ly5-eML3zTs-_fNX3D5Q",
--       "ciphertext": "Q8NLmeac9JhLh0CQPuG_7D9wVDb55eToCh0g5-FQ4M0",
--       "tag": "slzlo6-J9C7wSDF4dh_kBg"
--     }

-- Now decrypt......................................

-- First, load the JWE..
local jwe2 = chilkat.Jwe.new()
local success = jwe2:load_jwe(strJwe)
if not success then
    print(jwe2.last_error_text)
    return
end

-- Set the AES wrap key..
recipientIndex = 0
jwe2:set_wrapping_key(recipientIndex, aesWrappingKey, "base64url")

-- Decrypt
local originalPlaintext = jwe2:decrypt(recipientIndex, "utf-8")
if not jwe2.last_method_success then
    print(jwe2.last_error_text)
    return
end

print("original text decrypted with AES key wrap key: ")
print(originalPlaintext)

-- ---------------------------------------------------------------------------------
-- It should also be possible to decrypt the flattened JWE as shown in RFC 7516, Appendix A.5
-- because it was produced using the same key.

local sbJwe = chilkat.StringBuilder.new()

sbJwe:append("{")
sbJwe:append("\"protected\":")
sbJwe:append("\"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0\",")
sbJwe:append("\"unprotected\":")
sbJwe:append("{\"jku\":\"https://server.example.com/keys.jwks\"},")
sbJwe:append("\"header\":")
sbJwe:append("{\"alg\":\"A128KW\",\"kid\":\"7\"},")
sbJwe:append("\"encrypted_key\":")
sbJwe:append("\"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ\",")
sbJwe:append("\"iv\":")
sbJwe:append("\"AxY8DCtDaGlsbGljb3RoZQ\",")
sbJwe:append("\"ciphertext\":")
sbJwe:append("\"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY\",")
sbJwe:append("\"tag\":")
sbJwe:append("\"Mz-VPPyU4RlcuYv1IwIvzw\"")
sbJwe:append("}")

success = jwe2:load_jwe_sb(sbJwe)
if not success then
    print(jwe2.last_error_text)
    return
end

recipientIndex = 0
jwe2:set_wrapping_key(recipientIndex, aesWrappingKey, "base64url")

originalPlaintext = jwe2:decrypt(recipientIndex, "utf-8")
if not jwe2.last_method_success then
    print(jwe2.last_error_text)
    return
end

print("original text decrypted from published flattened JWE: ")
print(originalPlaintext)

-- The output:

-- original text decrypted with AES key wrap key:
-- Live long and prosper.
-- original text decrypted from published flattened JWE:
-- Live long and prosper.