1.FILE="yourapp.apk "

cert_XSA=`jar tf $FILE | grep SA '

The cert_XSA obtained at this time may be META-INF/*. RSA or META-INF/*.DSA.

2. Extract a specific signature file from 2.apk.

jar xf $FILE $cert_XSA

At this point, you will get the cert_XSA file in the current directory.