Modify the core.jar first.

Open core.jar.out/smali/java/security/MessageDigest.smali..

Search. Method public static isEqual, there is only one place.

. Method public static is equal([B[B]Z

. Locals 4

. Parameter "digesta"

. Parameter "digestb"

. preface

const/4 v 1，0x0

. Line 302

Array length v2, p0

Array length v3, p 1

if-eq v2，v3，:cond_ 1

. Line 3 10

.....

.....

.....

. Ending method

Delete everything below. Preface and above. End the method and keep it. Line XXX is below the first line. Delete the preface before.

Enter const/4 v0, 0x 1 on the following line. Line XXX (for example, I have line302 here), leave a blank line, and then enter return v0 in the next line.

It's like this after modification.

. Method public static is equal([B[B]Z

. Locals 1

. Parameter "digesta"

. Parameter "digestb"

. preface

. Line 302

const/4 v0，0x 1

Return to v0

. Ending method

protect

After this modification, apk can be installed as long as it is signed, regardless of whether the signed apk has been modified or not.