protectip from synplicity(in the synplify install directory) can encrypts VHDL and Verilog source files, it's a simple perl script which call the openssl for encryption.
The synplify tools can decrypt the source files before compiler, but the engineers can only read the encrypted text. so the ip be protected.
However, you can restore the source code if you got the password for ip encryption. I write the perl script for it.
Usage: decryptip
-in | input <Input File>
-out | output <Output File Name>
-c | cipher <Cipher - one of "des-cbc" "3des-cbc" "aes128-cbc">
-k | key <Symmetric Encryption Key in Text Format>
Example: ./decryptip -in protected_ip.v -out orig_ip.v -c des-cbc -k PASSWORD
