在/etc/apt/source.list中添加deepin的arm64的源
deb http://packages.deepin.com/aarch64 unstable main non-free contrib
但是执行apt-get update后就出错了，提升public key无效，LOG如下：
按照网上在key服务器中添加key也不行，有没有哪位热心GG了解的？可否帮忙指点一下，在此先谢过！

root@276bXXXXad51:/# apt-get update
Get:1 http://packages.deepin.com/aarch64 unstable InRelease [11.4 kB]
Hit:2 http://security.debian.org/debian-security buster/updates InRelease                                                  
Hit:3 http://deb.debian.org/debian buster InRelease                                          
Hit:4 http://mirrors.163.com/debian sid InRelease
Err:1 http://packages.deepin.com/aarch64 unstable InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 425956BB3E31DF51
Reading package lists... Done
W: GPG error: http://packages.deepin.com/aarch64 unstable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 425956BB3E31DF51
E: The repository 'http://packages.deepin.com/aarch64 unstable InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@276bXXXXad51:/# apt-key adv --recv-keys --keyserver keyserver.deepin.com 425956BB3E31DF51
Executing: /tmp/apt-key-gpghome.qo5rI3Bzb9/gpg.1.sh --recv-keys --keyserver keyserver.deepin.com 425956BB3E31DF51
gpg: keyserver receive failed: Connection timed out
root@276bXXXXad51:/# apt-key adv --recv-keys --keyserver keyserver.deepin.com 425956BB3E31DF51
Executing: /tmp/apt-key-gpghome.x5K2nETp9p/gpg.1.sh --recv-keys --keyserver keyserver.deepin.com 425956BB3E31DF51
gpg: keyserver receive failed: Connection timed out