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Use a signature to secure authenticity and data integrity for communicating with Trustly's API

Updated 1 month ago

Overview

The signature with private and public keys is used to ensure sender authenticity and data integrity.

All requests from the merchant shall be signed with the merchant's private key, Trustly will verify the signature of the request using the merchant's public key.
All responses from Trustly are signed with Trustly's private key and should be verified by the merchant using Trustly's public key.

Key generation

You can generate your private and public keys with OpenSSL:

If you are using Windows you will have to install OpenSSL for Windows in order to run the OpenSSL commands above.

The file public.pem should then be sent to the integration team at Trustly (integration@trustly.com).

Private

Public

openssl genrsa -out private.pem 2048

openssl rsa -pubout -in private.pem -out public.pem -outform PEM

Trustly's public keys

Trustly's public keys for TEST and LIVE.

TEST

LIVE

Serialising and signing your request

The signature is a Base64 encoding of the [Method, concatenated with UUID, concatenated with a serialisation of the Data{} object]. The serialisation is done by concatenating all scalars, hash keys, hash values and array values together, sorted ASCIIbetically. ("Null" is treated as an empty string.)

Please see the simple PHP example below for clarification, and try our signature tester, it will show you how to serialise and sign any data.

Serialise and signing

function serialize_data($object) {
    $serialized = '';
    if( is_array($object) ) {
        ksort($object); //Sort keys
        foreach($object as $key => $value) {
            if(is_numeric($key)) { //Array
                $serialized .= serialize_data($value);
            } else { //Hash
                $serialized .= $key . serialize_data($value);
            }
        }
    } else return $object; //Scalar
    return $serialized;
}

function sign($method, $uuid, $data) {
    $merchant_private_key = openssl_get_privatekey(file_get_contents(
                                'merchant_private_key.pem'
                            ));
    $plaintext = $method . $uuid . serialize_data($data);
    openssl_sign($plaintext, $signature, $merchant_private_key);
    return base64_encode($signature);
}

function verify($method, $uuid, $data, $signature_from_trustly) {
    $trustly_public_key = openssl_get_publickey(file_get_contents(
                                'trustly_public_key.pem'
                            ));
    $plaintext = $method . $uuid . serialize_data($data);
    return openssl_verify($plaintext,
                            base64_decode($signature_from_trustly),
                            $trustly_public_key
                         );
}

Below is an example of a JSON object and how it should be serialised:

Data structure

{
    "MyKey": "MyValue",
    "MyArray": [
        "Element1",
        "Element2",
        {
            "mykey2": "myvalue2"
        }
    ]
}

The JSON data above would result in the serialised string below:

Serialised string

MyArrayElement1Element2mykey2myvalue2MyKeyMyValue

API URL

Error handling

Authentication

Overview

Key generation

Trustly's public keys

Serialising and signing your request

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