Data Encryption and Decryption

In your Instnt JavaScript agent workflow configuration, you will configure the public part of a Public-Private RSA keypair. The private part of the keypair, which only you possess, is required to decrypt the data. The security of the keys is ensured by signing them with RSASSA-PKCS1-v1_5 SHA256 and encrypting them with RSA-OAEP for key wrapping and AES GCM for payload encryption. It's important to note that both of these processes require a minimum key length of 2048 bytes.

Generate Keys

To begin, generate a 4096-bit RSA key pair named private.pem, which encrypts a passphrase using the AES256 cipher:

% openssl genrsa -aes256 -out private.pem 4096
Generating RSA private key, 4096 bit long modulus
.............................................................
..............................................................++
..........................................................................................++
e is 65537 (0x10001)
Enter pass phrase for private.pem:
Verifying - Enter pass phrase for private.pem:

Public Key

To create a workflow, you need to extract the public key from the encrypted bundle created earlier. This can be done in a Privacy Enhanced Mail (PEM) format, which is a Base64 encoded DER certificate. PEM certificates are commonly used for web servers, as they can be easily translated into readable data using a simple text editor.

When a PEM encoded file is opened in a text editor, it includes specific headers and footers, as shown below:

% openssl rsa -in private.pem -outform PEM -pubout -out public.pem
Enter pass phrase for private.pem:
writing RSA key
% cat public.pem
-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----

To properly configure the workflow, you must copy and paste the complete public.pem key generated earlier, which includes the "BEGIN PUBLIC KEY" and "END PUBLIC KEY" header and footer, into the Encryption Management section located in the Security pane of Instnt's workflow builder, as shown below:
Screen

Decrypting and Verifying the JWE Token

After a potential customer submits their information through your website's workflow fields, your business will receive onboarding decisions and assertion details in a secure JWT container format. To access this information, you must decrypt and validate the container. The JWT specification is supported by several programming languages, such as Python, Node.js, and Java.

To decrypt the JWE token, your business' private PKI key is used in the first step. In the second step, the JWS token signature enclosed in the container is verified as being issued by Instnt. This verification process uses the public portion of the Instnt signing key which is shared with you:

To resume the onboarding workflow after receiving the Instnt decision callback, you need to retrieve the user assertion from the Instnt Assertion API by using the instntid UUID reference provided in the Decision Callback payload. Instnt will provide a reference with a redirect URL for you to proceed with the next step in your business' onboarding process.

Before accessing the instntid, the instntjwt token must be decrypted. The instntid is then used as an input for the GetAssertion function, as described in the Analyzing the Assertion Response documentation.

Here are some decryption and verification examples written in Python and Node.js frameworks:

from authlib.jose import JsonWebEncryption
from authlib.jose import JsonWebSignature
from authlib.jose import JWE_ALGORITHMS
 
# JWE token
JWE = 'eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.Tst5foFWOBfhGiKSBse3R3...'
 
# Read customer private key
with open('private.pem', 'r') as f:
 private_key = f.read()
 
# Decrypt JWE
jwe = JsonWebEncryption(algorithms=JWE_ALGORITHMS)
jwe_decrypted = jwe.deserialize_compact(JWE, private_key)
 
# Read Instnt public key
with open('instnt_kms_public.pem', 'r') as file:
 instnt_kms_public_pem = file.read()
 
# Validate JWS 
jws = JsonWebSignature(algorithms=['RS256'])
assertion = jws.deserialize_compact(jwe_decrypted['payload'], instnt_kms_public_pem)
json.loads(assertion['payload'].decode('utf-8'))
 
# {'iss': 'https://instnt.org', 'aud': 'https://acmebank.org', ..., 'instntid': '90205512-586d-4637-86cd-b63b582e480c'}

var jose = require('node-jose');
var fs = require('fs');
 
// JWE token
var JWE = 'eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.Tst5foFWOBfhGiKSBse3R3...'
 
// Read customer private key
var private_pem = fs.readFileSync('private.pem', 'utf8');
var private_key;
jose.JWK.asKey(private_pem, 'pem').
 then(function(result) {
 private_key = result;
 });
 
// Decrypt JWE
var jwe_decrypted;
jose.JWE.createDecrypt(private_key).
 decrypt(jwe).
 then(function(result) {
 jwe_decrypted = result;
 });
 
// Read Instnt public key
var instnt_kms_public_pem = fs.readFileSync('instnt_kms_public.pem', 'utf8');
var instnt_public_key;
jose.JWK.asKey(instnt_kms_public_pem, 'pem').
 then(function(result) {
 instnt_public_key = result;
 });
 
// Validate JWS
var assertion;
jose.JWS.createVerify(instnt_public_key).
 verify(jws).
 then(function(result) {
 assertion = result;
 });
 
assertion.payload.toString()
// {'iss': 'https://instnt.org', 'aud': 'https://acmebank.org', ..., 'instntid': '90205512-586d-4637-86cd-b63b582e480c'}

import com.nimbusds.jose.crypto.RSADecrypter;
import com.nimbusds.jose.crypto.RSASSAVerifier;
import com.nimbusds.jose.JWSVerifier;
import com.nimbusds.jose.jwk.JWK;
import com.nimbusds.jose.jwk.RSAKey;
import com.nimbusds.jwt.EncryptedJWT;
import com.nimbusds.jwt.SignedJWT;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;

public class JWTDecryptVerify
{
    public static void main(String[] args) throws Exception
    {
        String jwe = "eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ....";
        
        // Customer private encryption key
        String private_pem = new String(Files.readAllBytes(Paths.get("private.pem")),
                                             StandardCharsets.UTF_8);
        JWK private_key = JWK.parseFromPEMEncodedObjects(private_pem);
        RSADecrypter decrypter = new RSADecrypter((RSAKey) private_key);        
        
        // Decrypt
        EncryptedJWT jweObject = EncryptedJWT.parse(jwe);
        jweObject.decrypt(decrypter);        

        // Instnt public signing key
        String instnt_kms_public_pem = new String(Files.readAllBytes(Paths.get("instnt_kms_public.pem")),
                                                  StandardCharsets.UTF_8);
        JWK instnt_kms_public_key = JWK.parseFromPEMEncodedObjects(instnt_kms_public_pem);
        JWSVerifier verifier = new RSASSAVerifier((RSAKey) instnt_kms_public_key);        
        
        // Verify
        SignedJWT signedJWT = jweObject.getPayload().toSignedJWT();
        if (signedJWT.verify(verifier)) {
            System.out.println(signedJWT.getJWTClaimsSet());
        } else {
            System.err.println("Not verified!");
        }
    }
}

The token format and unwrapping process remain the same for both the assertion reference on the callback and the assertion itself, as explained in the Analyzing the Assertion Response documentation.

Data Encryption and Decryption

Generate Keys

Public Key

Decrypting and Verifying the JWE Token

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