debian更新时提示错误

[Guo Liang <blue_stone@xinhuanet.com>]

 我使用apt-get update进行更新的时候提示如下错误

W: GPG error: http://debian.ustc.edu.cn unstable Release: The following 
signatures couldn't be verified because the public key is not available: 
NO_PUBKEY 010908312D230C5F
W: You may want to run apt-get update to correct these problems

如果安装某软件包的话，提示如下错误：

Reading package lists... Done
Building dependency tree... Done
Recommended packages:
  ladspa-plugin sfftw2 fftw2-single
The following NEW packages will be installed:
  glame
0 upgraded, 1 newly installed, 0 to remove and 209 not upgraded.
Need to get 819kB of archives.
After unpacking 2175kB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
  glame
Install these packages without verification [y/N]? y
Get:1 http://mirror.pacific.net.au sid/main glame 2.0.1-2 [819kB]
Fetched 819kB in 20s (39.1kB/s)
Selecting previously deselected package glame.
(Reading database ... 170033 files and directories currently installed.)
Unpacking glame (from .../glame_2.0.1-2_i386.deb) ...
Setting up glame (2.0.1-2) ...

请问出了什么问题，怎么解决？
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