All official builds from LineageOS are signed with our private keys. You can verify a build has been signed with our keys by running:
keytool -list -printcert -jarfile lineage-build-signed.zip
The resulting fingerprints are listed as follows:
Certificate fingerprints: MD5: F2:CA:AA:A7:2F:D6:34:FE:70:D7:5C:41:43:6C:5E:14 SHA1: 9B:6D:F9:06:2A:1A:76:E6:E0:07:B1:1F:C2:EF:CB:EF:4B:32:F2:23 SHA256: 51:83:25:EF:7F:96:C0:D1:19:4C:2E:85:6B:04:0D:63:61:66:FF:B8:46:71:7D:72:FA:87:F4:FA:E5:BE:7B:BB
For the paranoid, the contents of this page are stored on github here.