Apt-get update says weak encryption

[Navjot Singh]

Whenever I run apt-get update command on Ubuntu, I get the following message

W: http://rpms.litespeedtech.com/debian/dists/xenial/Release.gpg: Signature by key 42259994257E19EB6A91CA853F6F627083084D0E uses weak digest algorithm (SHA1)
W: Invalid 'Date' entry in Release file /var/lib/apt/lists/rpms.litespeedtech.com_debian_dists_xenial_Release

Please look into it.