解码前：

Dim signedCred As String= "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"

Dim signedFromUmt As String = System.Text.Encoding.GetEncoding("utf-8").GetString(Convert.FromBase64String(signedCred))

解码后：

<SignedEnvelope> <content><![CDATA[ <UserCredentialEnvelope> <authAppId>umt</authAppId> <user> <displayName>管理员</displayName> <email></email> <name>admin@root.umt</name> <authBy>umt</authBy> </user> <validTime>2014-07-23 01:38:33</validTime> </UserCredentialEnvelope>]]> </content> <signature> qQoU9QKMjlmxlS5j4G23WY5RpPHL1AcVCvHvKMV8cucUoe7Ns8f5ll+yjZ9GrLsthJRCOrOV6y9l/1SOE04rNYBtUw9LeHSq5F5001I9lzrBEG17siuBPH+xyU/p4ONUmUq+2gzlGSfdqJhn95yNTUMgw2vK7v8r9Tgbnypb8C8= </signature> <appId>umt</appId> </SignedEnvelope>