微信开放平台 创建移动应用 Android 应用签名

keystore file decide it.

In fact, it is MD5 value of the keystore file.
please refer https://errong.win/generate-keystore/ to generate the keystore file.
You can get the MD5 via
keytool -list -v -keystore webrowser.keystore
MD5: 4F:87:B6:11:A4:37:5A:29:E4:A2:F7:BD:2B:DC:CC:18
Remove all ":" and turn the string to lower case.
Application signature is :
4f87b611a4375a29e4a2f7bd2bdccc18