Stripe: Payments can be made through Visa, MasterCard or American Express. No fee is charged for card payments. Read more about Stripe here.
Klarna: Pay via invoice (Sweden only). Read the terms here: Invoice or Part payment
Stripe has been audited by a PCI-certified auditor, and is certified to PCI Service Provider Level 1. This is the most stringent level of certification available. All card numbers are encrypted on disk with AES-256. Decryption keys are stored on separate machines. None of Stripe’s internal servers and daemons are able to obtain plaintext card numbers; instead, they can just request that cards be sent to a service provider on a static whitelist.
Stripe’s infrastructure for storing, decrypting, and transmitting card numbers runs in separate hosting infrastructure, and doesn’t share any credentials with Stripe’s primary services (API, website, etc.).