General FAQ & Troubleshooting

Current Release Information

December 21, 2021


  • HSM6 updated to 06.01.23Rel. Firmware is not field upgradeable
  • HSM4: 04.01.07RelHSM. No change
  • ZYMKEY4: 04.01.06RelE. No change

Zymbit Host Side Code:

  • libzk 1.1-21 (updated)
  • libzymkeyssl 1.0.10
  • zkapputilslib 1.1-22 (updated)
  • zkbootrtc 1.1-14
  • zkifc 1.2-32 (updated)
  • zkpkcs 1.0-2
  • zksaapps 1.0.14
  • zku 1.0.29 (updated)

New Features

Raspberry PI OS Bullseye

Added support for Raspberry PI OS Bullseye (32 bit). All Zymbit modules.

HD Wallet - Edwards Curve Support

HSM6: HD Wallet added ED25519 (edwards curve) support, as well as a “Cardano” specific variant.

HD Wallet - Oversight Wallet

HSM6: Includes new feature of Oversight Wallet. An Oversight Wallet allows a manager or overseer to monitor transactions without the ability to actually complete transactions.

HD Wallet - HD Wallet Shamir’s Secret Sharing

HSM6: Includes HD Wallet SLIP39 recovery, Shamir’s Secret Sharing, of up to 14 groups, each capable of 14 members. Shamir’s Secret Sharing is detailed here: Learn about SLIP-39

Known Issues

CPU Scaling Governor

We have seen some issues with the scaling cpu governor on the raspberry pi interfere with the i2c bus. This sometimes causes the zymkey to be put into a odd state or return failures from operations that get optimized out by the governor. The raspberry pi sets the scaling governor to be “ondemand” by default. We recommend switching this mode to “performance” to get the best out of the zymkey. Details:


When encrypting your rootfs, we highly recommend turning off unattended-upgrades prior to the encryption process. In some cases primarily with Ubuntu 20.04, during an update/upgrade after encryption, the update-initramfs process may fail and leave the system unable to boot.

To mitigate this issue, remove the service unattended-upgrades:

systemctl stop unattended-upgrades

systemctl disable unattended-upgrades


Q: Where can I learn about and/or pre-order future products?
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A: Sign up for our new product email updates at the bottom of Zymbit’s homepage.

Q: What are the differences between Zymbit’s Products?
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A: See the Product Comparison Matrix for the differences between Zymkey, HSM4, and HSM6. Please reach out with any further questions.

Q: How much power do Zymbit products consume?
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  • Zymkey-RPi (3.3V): idle approx. 1mA; max active < 25mA with LED off, < 35mA with LED on.
  • Zymkey-USB (5V): idle approx. 1.5mA; max active < 40mA with LEDs off, < 60mA with LEDs on.

See Power Quality for more information.


Q: Which operating systems does Zymbit support?
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supported OSs

Q: Which SBCs are compatible with Zymbit Products?
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  • Electrically, the Zymkey-I2C will interface to any single board computer using I2C. Check compatibility with your particular Linux distribution.
  • Raspberry Pi 3, 3B+, 4, Zero
  • RPi Compute Module 3, 4
  • NVIDIA Jetson Nano, Xavier NX

Q: Do Zymbit Products work with Arduino?
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A: We have no plans to release an Arduino shield version. While we love Arduinos and use them all the time, they generally don’t have enough resources to handle cryptographic operations at this level.

Q: Do Zymbit Products work with BeagleBone?
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A: Zymbit does not officially support the BeagleBoard platform at this time.