Why can I mount and read an encrypted home from another linux installation, without asking for a password?

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http://askubuntu.com – Not only is home directory encryption veery noticeably affecting performance on my laptop (early C2D), but I also just discovered, that I can mount and read files on that "encrypted" home when booting my PC from another linux installation without the password being asked! I basically have two questions: wtf?? this approach is flawed and is dangerous, since it gives false sense of security to the people. It is also terribly slow. Why is it still there? (HowTos)