Add an AES encryption and decryption example by stevenroose · Pull Request #111 · PointyCastle/pointycastle

stevenroose · 2017-01-27T19:15:32Z

No description provided.

Cretezy

Great work! I think this library definitely needs example of common use case, and this is a great start to that goal

Cretezy · 2018-08-17T00:06:37Z

+void main() {
+  // Key must be multiple of block size (16 bytes).
+  var key = new Digest("SHA-256").process(
+      UTF8.encode("correct horse battery staple"));


Use new utf8 (lowercase). I would also highly recommend to set any non-reassigned values (like this one) as final instead, which is generally considered a good practice.

Also, since we're now in the Dart 2 age, I would remove all instances of new.

Cretezy · 2018-08-17T00:07:30Z

+  encryptionCipher.init(true, params);
+  Uint8List encrypted = encryptionCipher.process(UTF8.encode(message));
+
+  print("Encrypted: \n" + HEX.encode(encrypted));


Lower cased hex.

Cretezy · 2018-08-17T00:07:38Z

+
+  BlockCipher decryptionCipher = new PaddedBlockCipher("AES/CBC/PKCS7");
+  decryptionCipher.init(false, params);
+  String decrypted = UTF8.decode(decryptionCipher.process(encrypted));


utf8 again

Cretezy · 2018-08-17T00:08:25Z

+import "dart:convert";
+import "dart:typed_data";
+
+import "package:hex/hex.dart";


No need, use standard library (included in dart:convert).

I can't seem to find hex in here: https://api.dartlang.org/stable/2.0.0/dart-convert/dart-convert-library.html

Cretezy · 2018-08-17T00:08:34Z

 dev_dependencies:
  benchmark_harness: ">=1.0.4 <2.0.0"
  browser: ">=0.9.0 <0.10.0"
+  hex: ">=0.1.1 <1.0.0"


Use stdlib.

stevenroose · 2018-08-19T13:33:02Z

If you want, I'd accept a PR from you with the suggested changes :)

stevenroose · 2018-10-04T15:30:47Z

If someone could review the example, that would be appreciated!

Cretezy · 2018-10-04T15:43:21Z

I'll take a good look and fix/add to it when I have time! I have yet to upgrade to the newer version of the registry (was using the "take 1" re-implementation).

hoboris · 2018-10-23T00:04:01Z

Apologies for hijacking this pull request. I used your example code to encrypt a message with aes 256 and md5

// Key must be multiple of block size (16 bytes).
    var key = new Digest("MD5").process(
        utf8.encode("correcthorsebatterystaple"));
    // Can be anything.
    var message = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed d o eiusmod tempor incididunt ut labore et dolore magna aliqua.";
    // The initialization vector must be unique for every message, so it is a
    // good idea to use a message digest as the IV.
    // IV must be equal to block size (16 bytes).
    var iv = new Digest("MD5").process(utf8.encode(message)).sublist(0, 16);
    // The parameters your cipher will need. (PKCS7 does not need params.)
    CipherParameters params = new PaddedBlockCipherParameters(
        new ParametersWithIV(new KeyParameter(key), iv), null);
    print("Message: \n$message");
    ////////////////
    // Encrypting //
    ////////////////
    // As for why you would need CBC mode and PKCS7 padding, consult the internet
    // (f.e. http://www.di-mgt.com.au/properpassword.html).
    BlockCipher encryptionCipher = new PaddedBlockCipher("AES/CBC/PKCS7");
    encryptionCipher.init(true, params);
    Uint8List encrypted = encryptionCipher.process(utf8.encode(message));
    print("Encrypted: \n" + HEX.encode(encrypted));

It does decrypt well with your decryption method. But I tried to decrypt it with openssl with

echo "$encrypted" | openssl enc -d -aes-256-cbc -k $key -a -md md5
encrypted being the hexa encrypted message

But I get a bad magic number error. Am I mising something ?

stevenroose · 2018-10-23T11:55:03Z

I have no idea, tbh. Did that command work with an openssl encrypted message? (f.e. echo adds a newline, not sure if that could break things -- try printf)

It's quite possible that there is an issue with our implementation that we're not aware off. Did you try decrypting with BouncyCastle, f.e.?

hoboris · 2018-10-29T23:59:14Z

I have just tried with javax.crypto library and it is the same, so it must be something else I haven't figured out yet, but the problem does not lie with with PointyCastle or your example.

guoyuanzhuang · 2019-01-15T09:58:48Z

@Cretezy AES result is different with Java.
`public class AESUtil {

private static String AES_ALGORITHM = "AES/ECB/PKCS5Padding";
private static String CHAR_ENCODING = "UTF-8";

public static byte[] encrypt(byte[] data, byte[] key) {
	try {
		SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
		byte[] enCodeFormat = secretKey.getEncoded();
		SecretKeySpec seckey = new SecretKeySpec(enCodeFormat, "AES");
		Cipher cipher = Cipher.getInstance(AES_ALGORITHM);
		cipher.init(Cipher.ENCRYPT_MODE, seckey);
		byte[] result = cipher.doFinal(data);
		return result; // 加密
	} catch (Exception e) {
		e.printStackTrace();
	}
	return null;
}

public static byte[] decrypt(byte[] data, byte[] key) {
	try {
		SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
		byte[] enCodeFormat = secretKey.getEncoded();
		SecretKeySpec seckey = new SecretKeySpec(enCodeFormat, "AES");
		Cipher cipher = Cipher.getInstance(AES_ALGORITHM);
		cipher.init(Cipher.DECRYPT_MODE, seckey);
		byte[] result = cipher.doFinal(data);
		return result; // 加密
	} catch (Exception e) {
		e.printStackTrace();
	}
	return null;
}

public static String encrypt(String data, String key) {
	try {
		byte[] valueByte = encrypt(data.getBytes(CHAR_ENCODING),
				key.getBytes(CHAR_ENCODING));
		return new String(Base64.encode(valueByte, Base64.DEFAULT));
	} catch (Exception e) {
		e.printStackTrace();
	}
	return null;
}

public static String decrypt(String data, String key) {
	try {
		byte[] originalData = Base64.decode(data.getBytes(), Base64.DEFAULT);
		byte[] valueByte = decrypt(originalData,
				key.getBytes(CHAR_ENCODING));
		return new String(valueByte, CHAR_ENCODING);
	} catch (UnsupportedEncodingException e) {
		e.printStackTrace();
	}
	return null;
}

public static String parseByte2HexStr(byte buf[]) {
	StringBuffer sb = new StringBuffer();
	for (int i = 0; i < buf.length; i++) {
		String hex = Integer.toHexString(buf[i] & 0xFF);
		if (hex.length() == 1) {
			hex = '0' + hex;
		}
		sb.append(hex.toUpperCase());
	}
	return sb.toString();
}

}
`
What went wrong? thank you

guoyuanzhuang · 2019-01-16T11:00:13Z

It's solved
thank you

SopheapSK · 2019-04-20T08:56:49Z

@Cretezy AES result is different with Java.
`public class AESUtil {

private static String AES_ALGORITHM = "AES/ECB/PKCS5Padding";
private static String CHAR_ENCODING = "UTF-8";

public static byte[] encrypt(byte[] data, byte[] key) {
	try {
		SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
		byte[] enCodeFormat = secretKey.getEncoded();
		SecretKeySpec seckey = new SecretKeySpec(enCodeFormat, "AES");
		Cipher cipher = Cipher.getInstance(AES_ALGORITHM);
		cipher.init(Cipher.ENCRYPT_MODE, seckey);
		byte[] result = cipher.doFinal(data);
		return result; // 加密
	} catch (Exception e) {
		e.printStackTrace();
	}
	return null;
}

public static byte[] decrypt(byte[] data, byte[] key) {
	try {
		SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
		byte[] enCodeFormat = secretKey.getEncoded();
		SecretKeySpec seckey = new SecretKeySpec(enCodeFormat, "AES");
		Cipher cipher = Cipher.getInstance(AES_ALGORITHM);
		cipher.init(Cipher.DECRYPT_MODE, seckey);
		byte[] result = cipher.doFinal(data);
		return result; // 加密
	} catch (Exception e) {
		e.printStackTrace();
	}
	return null;
}

public static String encrypt(String data, String key) {
	try {
		byte[] valueByte = encrypt(data.getBytes(CHAR_ENCODING),
				key.getBytes(CHAR_ENCODING));
		return new String(Base64.encode(valueByte, Base64.DEFAULT));
	} catch (Exception e) {
		e.printStackTrace();
	}
	return null;
}

public static String decrypt(String data, String key) {
	try {
		byte[] originalData = Base64.decode(data.getBytes(), Base64.DEFAULT);
		byte[] valueByte = decrypt(originalData,
				key.getBytes(CHAR_ENCODING));
		return new String(valueByte, CHAR_ENCODING);
	} catch (UnsupportedEncodingException e) {
		e.printStackTrace();
	}
	return null;
}

public static String parseByte2HexStr(byte buf[]) {
	StringBuffer sb = new StringBuffer();
	for (int i = 0; i < buf.length; i++) {
		String hex = Integer.toHexString(buf[i] & 0xFF);
		if (hex.length() == 1) {
			hex = '0' + hex;
		}
		sb.append(hex.toUpperCase());
	}
	return sb.toString();
}

}
`
What went wrong? thank you

my code in java is exactly the same as yours. but I still cannot find the way to configure code in dart to work as java yet. the result is different.

simbados · 2019-09-04T11:00:45Z

+  // The initialization vector must be unique for every message, so it is a
+  // good idea to use a message digest as the IV.
+  // IV must be equal to block size (16 bytes).
+  var iv = new Digest("SHA-256").process(utf8.encode(message)).sublist(0, 16);


Taking the hash of the plaintext for the IV might not be a good idea, as it leaks information about the plaintext. If the text is encrypted twice the IV will be the same. Might be better to use a PRNG.

izaera · 2020-12-23T09:16:06Z

I'm archiving this repo as per #239 (see the issue for more info).

Cretezy suggested changes Aug 17, 2018

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stevenroose force-pushed the aes-example branch from 2a6412f to 9974354 Compare October 4, 2018 15:30

Add an AES encryption and decryption example

9974354

This was referenced Oct 4, 2018

AES result is different with aes-js or nodejs #154

Closed

AES Encrypt、Decrypt #142

Open

simbados reviewed Sep 4, 2019

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