OCRA OTP Card - Product specs


This page describes the physical properties and constrains of the OCRA OTP cards.

Read this document to learn about the technical configuration and the possibilities to customize the cards.


After activation, the display requests the user to input an 8-digit challenge. The user then enters a configurable 4-digit PIN. The card responds with a 6-digit response that is displayed for 20 seconds. In the last step the user enters the response into the interface that generated the challenge where it is verified.


Card Components

    • 6-digit 7-segment LCD
      • 13-button keypad
        • Battery
          • Microprocessor
            • NFC Interface



                The card is sized in the commonly used ISO/IEC 7810 ID-1 format (85.60 × 53.98 mm), common for credit and banking cards. They are 0.76 - 0.8 mm in height plus a minimal layer of printed color.



                The card is made of plastic and the UV fixed ink is resistant to scratches. To avoid accidental activation, a case is delivered with each card. The card can be bend like a regular credit card.




                  By default the cards run the algorithm suite OCRA-1:HOTP-SHA1-6:C-QN08-PSHA1, on request the used algorithm can be changed for a batch of cards to one of the following modes:

                  • OCRA-1:HOTP-SHA1-6:QN08
                  • OCRA-1:HOTP-SHA1-6:C-QN08
                  • OCRA-1:HOTP-SHA1-6:QN08-PSHA1
                  • OCRA-1:HOTP-SHA1-6:C-QN08-PSHA1 (default)

                  The used algorithm impacts the number of possible activations for a card. The secrets are initialized randomly for each card but can be customized on request.


                  Each card is provisioned with a 20 Byte random unique secret, which will be provided on delivery. Cloned cards that share a secret can be ordered on request.

                  The authentication PIN used for the challenge response handshake is not stored on the card. The 4-digit PIN can be freely selected by the user on a case-by-case basis.


                  Lifespan / Power usage

                    The number of possible activations for a card depends on:


                    • Used algorithm
                    • Amount of time the display shows content
                    • Environmental aspects, such as temperature

                    The default display activation time is 20 seconds and can be set between 10 and 60 seconds for custom cards.

                    The recommended operational environment is 20 degree Celsius.



                    OTP.to cards are printed with an UV color ink printer. Each layer of ink adds ~0.04 mm to the height. For designs we primarily use colors from the Roland Color System and texture libraries.


                    Design & Layout

                    The card design can either be a ready to use one from the catalog or you can choose to create your own custom design for your organization and use case. The visual parts that make up a card are:

                    • Keyboard and power button are printed with an additional structural layer to improve tactile feedback
                    • An optional random ID, can be used to identify the card in your system
                    • Different color schemes can be selected for the available designs to signal different classes of importance
                    • The back of the card can be completely used but should include the battery symbol for correct e-waste disposal

                    Custom Design

                    OTP.to can print custom designs for your use case and organization. We have Adobe Illustrator templates ready to share with your design department. We can assist in creating a design if we are provided with style guides and logos in vector formats. If you create your own design OTP.to will guide you and point out learned lessons in creating production ready designs. For requests of custom designed prints please contact us.

                    The buttons are on a fixed position an cannot be moved.

                    Additional documentation on how to develop a design is available on request.