The USB devices communicate with the host computer using the human interface device (HID) protocol, essentially mimicking a keyboard. Therefore, for services that do not provide any alternate account recovery method, the use of U2F should be carefully considered. If a hardware duplicate or alternate hardware key is not kept and the original U2F hardware key is lost, no recovery of the key is possible (because the private key exists only in hardware). In terms of disadvantages, one significant difference and potential drawback to be considered regarding hardware-based U2F solutions is that unlike with TOTP shared secret methods, there is no possibility of 'backing up' of recovery codes or shared secrets. Transmission / creation of authentication code is via USB or NFC between hardware key and computer without manual typing steps.Plaintext code is displayed and typed by user manually, visually.Challenge / response is signed (encoding originating domain/website) to prevent interception and reuse.Plaintext code response vulnerable to interception and MITM attack if user has been phished by malicious website.Private key only stored on user hardware device.Transmission of public key challenge / response.

Shared secret may be stored in plaintext on server.

Plaintext or QR code transmission of shared secret between server and user.

Specifically:Ĭomparison of security issues between TOTP and U2F 6-digit codes generated on Google Authenticator) were a significant improvement over SMS-based security codes, a number of security vulnerabilities were still possible to exploit, which U2F sought to improve. While Time-based one-time passwords (e.g. Please help improve it by integrating both sides into a more neutral presentation if this helps improve article flow. This section contains a pro and con list, which is sometimes inappropriate.

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