1. JDK version
openjdk version "1.8.0_302"
OpenJDK Runtime Environment (Temurin)(build 1.8.0_302-b08)
OpenJDK 64-Bit Server VM (Temurin)(build 25.302-b08, mixed mode)

2. Test.java
public class Test {

    public static void main(String[] args) {
        System.out.println(sun.security.util.AlgorithmDecomposer.class);
        System.out.println(sun.security.util.math.MutableIntegerModuloP.class);
    }
}

3. javac Test.java
Test.java:4: warning: AlgorithmDecomposer is internal proprietary API and may be removed in a future release
        System.out.println(sun.security.util.AlgorithmDecomposer.class);
                                            ^
Test.java:5: error: package sun.security.util.math does not exist
        System.out.println(sun.security.util.math.MutableIntegerModuloP.class);
                                                 ^
1 error
1 warning

sun.security.util.math package should be there
https://hg.openjdk.java.net/jdk8u/jdk8u-dev/jdk/file/tip/src/share/classes/sun/security/util/math/