These resources files are in Java classes. If converted to properties files, the localized versions can use UTF-8 encoding directly.

./src/java.base/share/classes/sun/security/tools/keytool/Resources.java
./src/java.base/share/classes/sun/security/util/Resources.java
./src/java.base/share/classes/sun/security/util/AuthResources.java
./src/jdk.jartool/share/classes/sun/security/tools/jarsigner/Resources.java