The only way to encrypt the data between Apache httpd and Tomcat is to use mod_proxy with https.

In httpd.conf you need something like:

SSLProxyEngine On
SSLProxyVerify require
SSLProxyCACertificateFile conf/cacert.pem
SSLProxyMachineCertificateFile conf/proxy.pem
ProxyPass /
ProxyPassReverse /
conf/proxy.pem should contain both key and certificate (and the certificate must be trusted by Tomcat).
conf/cacert.pem must contain the CA that signed the Tomcat certificate.