error al pasar de debian oldstable squeeze a estable wheezy

error al tratar de hacer upgrade de oldstable a estable
les
saldra algo como esto

# apt-get update
Get:1 http://ftp.ch.debian.org lenny Release.gpg [386B]
Hit http://ftp.ch.debian.org lenny Release
Ign http://ftp.ch.debian.org lenny/main Packages/DiffIndex
Ign http://ftp.ch.debian.org lenny/main Sources/DiffIndex
Hit http://ftp.ch.debian.org lenny/main Packages
Hit http://ftp.ch.debian.org lenny/main Sources
Hit ftp://ftp.de.debian.org lenny Release.gpg
Get:2 http://security.debian.org lenny/updates Release.gpg [189B]
Get:3 ftp://ftp.de.debian.org lenny Release [63.2kB]
Hit http://security.debian.org lenny/updates Release
Ign http://security.debian.org lenny/updates/main Packages/DiffIndex
Ign http://security.debian.org lenny/updates/contrib Packages/DiffIndex
Ign http://security.debian.org lenny/updates/non-free Packages/DiffIndex
Get:4 ftp://ftp.de.debian.org lenny/main Packages/DiffIndex
Ign ftp://ftp.de.debian.org lenny/main Packages/DiffIndex
Hit http://security.debian.org lenny/updates/main Packages
Get:5 ftp://ftp.de.debian.org lenny/contrib Packages/DiffIndex
Ign ftp://ftp.de.debian.org lenny/contrib Packages/DiffIndex
Get:6 ftp://ftp.de.debian.org lenny/non-free Packages/DiffIndex
Hit http://security.debian.org lenny/updates/contrib Packages
Ign ftp://ftp.de.debian.org lenny/non-free Packages/DiffIndex
Hit ftp://ftp.de.debian.org lenny/main Packages
Hit ftp://ftp.de.debian.org lenny/contrib Packages
Hit ftp://ftp.de.debian.org lenny/non-free Packages
Hit http://security.debian.org lenny/updates/non-free Packages
Fetched 63.2kB in 1s (40.2kB/s)
Reading package lists... Done
W: There is no public key available for the following key IDs:
4D270D06F42584E6
W: There is no public key available for the following key IDs:
4D270D06F42584E6
W: You may want to run apt-get update to correct these problems

solucion

# gpg --export  4D270D06F42584E6 | apt-key add

# apt-key update



fuente:

http://www.linuxquestions.org/questions/debian-26/there-is-no-public-key-available-for-the-following-key-id-705108/