RPMs are now signed and the public key is included in the bundle, located in the Linux/i386-x8664/signing directory. If the TTU installer (setup.bat) is used to install, then the public key is imported before any packages are installed. If not, then please use the importkey.sh script to import the public key before installing.
The public key is also located at https://access.teradata.com/resources/html/signingkey.html. There is information on the website to verify the key before importing it.