powerpath encryption

Other recommended reading would be the Whitepaper "EMC PowerPath Encryption with RSA - Best Practices Planning" and also whitepaper "Approaches for Encryption of Data-at-Rest in the Enterprise - a detaileds review"

Both are available on PowerLink under

Home > Support > Technical Documentation and Advisories > White Papers >

Once you have migrated to encrypted virtual logical unit, the data on that device is encrypted, the data can only be read by the hosts that have the RSA key to unlock the cipher. All versions of PowerPath, starting in v5.2, will contain the RSA encryption feature. So you will not have the issue of a version of PowerPath being unable to read the data unless its a downgrade to a version that does not have the RSA feature.
Once the data is encrypted on a virtual logical unit, to return to an unencrypted volume you need to user PowerPath Migration Enabler (PPME) feature to migrate fromt he encrypted volume to an unencrypted volume.

All process steps are documented well in
EMC PowerPath Encryption with RSA Version 5.2 for Solaris and Windows
USER GUIDE P/N 300-006-408 REV A03
available on PowerLink.

i heard of that powerpath in encryption mode can work with some LVM software, since data is encrypted, how could these LVM translate the data? maybe only data is encrypted, but meta-data(control data) is not, is my understanding correct?

There are special considerations for each LVM product, each of these is dealt in the Volume Manager section (page30) of the "EMC® PowerPath® Encryption with RSA® version 5.2 for Solaris and Windows guide" from my first reply.