Howto enable NTP autokey on CentOS7 with RSA-MD5
New version of RedHat server O.S. breaks compatibility with old versions of NTP server
To make old RSA-MD5 keys generation and usage with newer versions of RedHat/CentOS openssl (1.0.1e), you have to set an environment variable:
OPENSSL_ENABLE_MD5_VERIFY=1
both when you invoke ntp-keygen and on server start (by setting it in /etc/default/ntpd)