hola tuxeros necesito ayuda con este error por fa, estoy intentando instalar skype en centos4.4

[root@mateo skype]# yum -y install libsigc++ libstdc
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
No Match for argument: libstdc
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Package libsigc++.i386 0:1.2.5-4.2.el4.rf set to be updated
--> Running transaction check

Dependencies Resolved

=============================================================================
 Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
 libsigc++               i386       1.2.5-4.2.el4.rf  dag apt            37 k

Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)
Total download size: 37 k
Downloading Packages:
warning: rpmts_HdrFromFdno: V3 DSA signature: NOKEY, key ID 6b8d79e6


Public key for libsigc++-1.2.5-4.2.el4.rf.i386.rpm is not installed