Pretty Good Privacy: “Encryption Software not Compression Programs:

In a post of 14 Feb 2005 entitled, “Why Word and Excel Password Protection Are Not Safe”, I quoted a ZDNet recommendation that users, use compression programs to protect their private files.
However, reader John Dasher, Director, Product Management, PGP Corporation (Pretty Good Privacy) writes:
Compression does not provide security. Some of the popular compression programs provide weak security password, but this brings with it a new problem in that MOST of these programs use proprietary security/encryption which would be typically classified as “weak”.
If people want to secure files, they should use encryption software (rather than compression software) like PGP Desktop, from PGP Corporation. PGP products are used by tens of thousands of global corporations to secure email and files. It is based on the mature and battle tested PGP Software Development Kit (SDK) cryptographic engine used by all PGP products, and source code for PGP products is publicly available for peer review.