I was bored so I figured out how Yahoo files are encoded. Mostly. - rob import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.nio.ByteOrder; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.util.Date; public class YahooDumper { public static void main(String[] args) { try { // Figure out who's talking. File in = new File(args[0]); String author = in.getName().substring(9, in.getName().length() - 4); String friend = in.getParentFile().getName(); String[] participants = { author, friend }; // The xor key is the chars from the author's name char[] key = author.toCharArray(); // Map the file in. FileChannel fc = new FileInputStream(in).getChannel(); MappedByteBuffer buf = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size()); buf.order(ByteOrder.LITTLE_ENDIAN); while (buf.hasRemaining()) { // The time is encoded in seconds. Date when = new Date(buf.getInt() * 1000L); // This value is always 6. I don't know what it means. int six = buf.getInt(); // This int always seems to be 0 or 1 ... it's possible that // everything other than the first bit is used for something else. int who = buf.getInt(); // The length may not be 4 bytes; there may be two shorts // here, only the first of which is used for length. int len = buf.getInt(); // Sometimes there are blank records here and there. So len is // really zero from time to time. if (len > 0) { System.out.print(when + "\t" + (participants[who]) + ": "); for (int i = 0; i < len; i++) { int c = buf.get() ^ key[i % key.length]; System.out.print((char) c); } System.out.println(); } // This always seems to be zero. buf.getInt(); } fc.close(); } catch (IOException e) { e.printStackTrace(); } } }