KB2026.610
FAQ: TM2000 PTP/NTP Server ntp.keys

Last Updated: 10 Jun 2026

Time Machines is a Nebraska-based manufacturer of highly resilient, low cost PTP/NTP appliances. This article describes some of the peculiarities of how this appliance handles its ntp.keys file for accepting signed time requests and signing time responses.

Time Machines offers several models. The one we examined in our labs was a TM2000, firmware version 0.6.6. Newer offerings may differ from the model we tested. We noticed some oddities, likely inherited from strict reliance on Dr. Mills' original NTPd specifications. Once you understand the behavior, establishing a working key store is relatively simple.

    TM2000 ntp.keys Limitations

    1. Only MD5 and SHA1 key types are supported

    2. MD5 keys cannot exceed 20 characters

    3. MD5 keys must be alphanumeric (no punctuation or special characters)

    4. SHA1 keys must be exactly 40 hex characters

    5. Stops parsing ntp.keys file if
      - Key numbers are not sequentially ascending
      - Any key is not supported

    6. When the TM2000 stops parsing the ntp.keys file, any remaining keys in the file are ignored, even if they meet the TM2000's restrictions

    Example Configurations

    CORRECT (Ascending order, Alphanumeric MD5, Hex SHA1)

    11 MD5 MySecretKey123
72 SHA1 a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2
73 MD5 AnotherSecret

    INCORRECT (Will stop parsing at line 2 due to punctuation, but even if you fix that, line 4 will be ignored due to non-ascending sequence)

    19 MD5 MySecretKey123
27 MD5 Bad_Key!
55 MD5 IgnoredKey
29 SHA1 a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2

We hope you find this information helpful, but urge you to contact the manufacturer if you have questions or want to inquire about newer models. We do not recommend any particular appliance. Available appliances range from very cheap to very expensive, and you must choose the appliance that suits your network's needs and regulatory compliance specifications.

Time Machines
300 S 68th St Place, STE 100
Lincoln, NE 68510

Phone: +1-402-486-0511
Fax: +1-206-339-8595

Website: https://timemachinescorp.com
Email: tmsales@timemachinescorp.com

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