230 lines
8.1 KiB
Java
230 lines
8.1 KiB
Java
/*
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* Copyright (C) 2012-2014 Dominik Schürmann <dominik@dominikschuermann.de>
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* Copyright (C) 2010-2014 Thialfihar <thi@thialfihar.org>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package org.sufficientlysecure.keychain.pgp;
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import android.content.Context;
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import android.graphics.Color;
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import android.text.Spannable;
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import android.text.SpannableStringBuilder;
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import android.text.style.ForegroundColorSpan;
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import org.spongycastle.openpgp.PGPPublicKey;
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import org.spongycastle.util.encoders.Hex;
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import org.sufficientlysecure.keychain.Constants;
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import org.sufficientlysecure.keychain.R;
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import org.sufficientlysecure.keychain.util.Log;
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import java.security.DigestException;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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import java.util.Locale;
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public class PgpKeyHelper {
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/**
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* TODO: Only used in HkpKeyServer. Get rid of this one!
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*/
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public static String getAlgorithmInfo(int algorithm) {
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return getAlgorithmInfo(null, algorithm, 0);
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}
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public static String getAlgorithmInfo(Context context, int algorithm) {
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return getAlgorithmInfo(context, algorithm, 0);
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}
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/**
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* Based on <a href="http://tools.ietf.org/html/rfc2440#section-9.1">OpenPGP Message Format</a>
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*/
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public static String getAlgorithmInfo(Context context, int algorithm, int keySize) {
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String algorithmStr;
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switch (algorithm) {
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case PGPPublicKey.RSA_ENCRYPT:
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case PGPPublicKey.RSA_GENERAL:
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case PGPPublicKey.RSA_SIGN: {
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algorithmStr = "RSA";
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break;
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}
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case PGPPublicKey.DSA: {
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algorithmStr = "DSA";
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break;
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}
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case PGPPublicKey.ELGAMAL_ENCRYPT:
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case PGPPublicKey.ELGAMAL_GENERAL: {
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algorithmStr = "ElGamal";
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break;
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}
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case PGPPublicKey.ECDSA:
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case PGPPublicKey.ECDH: {
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algorithmStr = "ECC";
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break;
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}
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default: {
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if (context != null) {
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algorithmStr = context.getResources().getString(R.string.unknown_algorithm);
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} else {
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// TODO
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algorithmStr = "unknown";
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}
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break;
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}
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}
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if (keySize > 0)
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return algorithmStr + ", " + keySize + " bit";
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else
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return algorithmStr;
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}
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/**
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* Converts fingerprint to hex (optional: with whitespaces after 4 characters)
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* <p/>
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* Fingerprint is shown using lowercase characters. Studies have shown that humans can
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* better differentiate between numbers and letters when letters are lowercase.
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*
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* @param fingerprint
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* @return
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*/
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public static String convertFingerprintToHex(byte[] fingerprint) {
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String hexString = Hex.toHexString(fingerprint).toLowerCase(Locale.US);
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return hexString;
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}
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/**
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* Convert key id from long to 64 bit hex string
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* <p/>
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* V4: "The Key ID is the low-order 64 bits of the fingerprint"
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* <p/>
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* see http://tools.ietf.org/html/rfc4880#section-12.2
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*
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* @param keyId
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* @return
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*/
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public static String convertKeyIdToHex(long keyId) {
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long upper = keyId >> 32;
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if (upper == 0) {
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// this is a short key id
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return convertKeyIdToHexShort(keyId);
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}
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return "0x" + convertKeyIdToHex32bit(keyId >> 32) + convertKeyIdToHex32bit(keyId);
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}
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public static String convertKeyIdToHexShort(long keyId) {
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return "0x" + convertKeyIdToHex32bit(keyId);
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}
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private static String convertKeyIdToHex32bit(long keyId) {
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String hexString = Long.toHexString(keyId & 0xffffffffL).toLowerCase(Locale.US);
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while (hexString.length() < 8) {
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hexString = "0" + hexString;
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}
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return hexString;
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}
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public static SpannableStringBuilder colorizeFingerprint(String fingerprint) {
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// split by 4 characters
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fingerprint = fingerprint.replaceAll("(.{4})(?!$)", "$1 ");
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// add line breaks to have a consistent "image" that can be recognized
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char[] chars = fingerprint.toCharArray();
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chars[24] = '\n';
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fingerprint = String.valueOf(chars);
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SpannableStringBuilder sb = new SpannableStringBuilder(fingerprint);
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try {
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// for each 4 characters of the fingerprint + 1 space
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for (int i = 0; i < fingerprint.length(); i += 5) {
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int spanEnd = Math.min(i + 4, fingerprint.length());
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String fourChars = fingerprint.substring(i, spanEnd);
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int raw = Integer.parseInt(fourChars, 16);
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byte[] bytes = {(byte) ((raw >> 8) & 0xff - 128), (byte) (raw & 0xff - 128)};
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int[] color = getRgbForData(bytes);
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int r = color[0];
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int g = color[1];
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int b = color[2];
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// we cannot change black by multiplication, so adjust it to an almost-black grey,
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// which will then be brightened to the minimal brightness level
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if (r == 0 && g == 0 && b == 0) {
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r = 1;
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g = 1;
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b = 1;
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}
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// Convert rgb to brightness
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double brightness = 0.2126 * r + 0.7152 * g + 0.0722 * b;
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// If a color is too dark to be seen on black,
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// then brighten it up to a minimal brightness.
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if (brightness < 80) {
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double factor = 80.0 / brightness;
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r = Math.min(255, (int) (r * factor));
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g = Math.min(255, (int) (g * factor));
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b = Math.min(255, (int) (b * factor));
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// If it is too light, then darken it to a respective maximal brightness.
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} else if (brightness > 180) {
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double factor = 180.0 / brightness;
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r = (int) (r * factor);
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g = (int) (g * factor);
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b = (int) (b * factor);
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}
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// Create a foreground color with the 3 digest integers as RGB
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// and then converting that int to hex to use as a color
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sb.setSpan(new ForegroundColorSpan(Color.rgb(r, g, b)),
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i, spanEnd, Spannable.SPAN_INCLUSIVE_INCLUSIVE);
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}
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} catch (Exception e) {
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Log.e(Constants.TAG, "Colorization failed", e);
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// if anything goes wrong, then just display the fingerprint without colour,
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// instead of partially correct colour or wrong colours
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return new SpannableStringBuilder(fingerprint);
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}
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return sb;
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}
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/**
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* Converts the given bytes to a unique RGB color using SHA1 algorithm
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*
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* @param bytes
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* @return an integer array containing 3 numeric color representations (Red, Green, Black)
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* @throws java.security.NoSuchAlgorithmException
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* @throws java.security.DigestException
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*/
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private static int[] getRgbForData(byte[] bytes) throws NoSuchAlgorithmException, DigestException {
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MessageDigest md = MessageDigest.getInstance("SHA1");
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md.update(bytes);
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byte[] digest = md.digest();
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int[] result = {((int) digest[0] + 256) % 256,
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((int) digest[1] + 256) % 256,
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((int) digest[2] + 256) % 256};
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return result;
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}
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}
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