Portage's cryptsetup needs libdevmapper.so.1.01 to be able to read the maps, otherwise crypted images will not mount with the error: "Command failed: Invalid argument" There seems to be a cryptsetup snapshot which adresses this issue, please see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=344313 As a temporary fix, masking '>=sys-fs/device-mapper-1.02.02' helps. This might affekt cryptsetup-luks as well, I have not tested it.
patch is here: http://bugs.debian.org/cgi-bin/bugreport.cgi/diff?bug=344313;msg=10;att=1
in cvs, thanks for reporting
This problem still exists in the AMD64 stable branch. device-mapper-1.02.02 has been marked stable on AMD64, however cryptsetup-0.1-r3 is still masked and cryptsetup-0.1-r2 (the current stable lead) doesn't work with device-mapper-1.02 versions as described. The solution is quite easy: Mark cryptsetup-0.1-r3 stable or mask device-mapper-1.02.02 again. Please reopen this bug (I don't have sufficient permissions for this).
reopenned. AMD plesae mark stable as per bug #124928
only alpha is left on bug 124928, removing amd64
fixed