如何计算Android本地已安装应用的MD5指纹并与服务端进行校验？

Question

有需求，要获取自身应用程序的签名，与服务器进行校验比对.
服务器保存的签名是直接从android包中提取出来的签名MD5指纹，如下：

而我本地通过网上搜寻的方法，获取到的签名信息的方法是这样子的：

 private String getSign(Context context) { 
        PackageManager pm = context.getPackageManager(); 
        List<PackageInfo> apps = pm.getInstalledPackages(PackageManager.GET_SIGNATURES); 
        Iterator<PackageInfo> iter = apps.iterator(); 
        while(iter.hasNext()) { 
             PackageInfo packageinfo = iter.next(); 
                return packageinfo.signatures[0].toCharsString(); 
     } 
        return null; 
    }

而得到的信息是样子的：

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

那么，我如何才能进行比对呢？

我对用Keytool获取到的签名信息的MD5指纹是怎么生成的并不了解，有些地方理解或许会有错误，请大神们不吝指教！

Answer 1

题主其实离目标就差一步了，题主把得到的这一堆字符串进行一次MD5或SHA1加密，得到的加密值就是题主要拿去比对校验的值(分别对应MD5和SHA1)，MD5及SHA1加密方法相信题主应该会或者会自己去查找写法。