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import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.SecureRandom;
import java.security.Security;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
public class MainClass {
public static void main(String[] args) throws Exception {
Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
SecureRandom random = new SecureRandom();
IvParameterSpec ivSpec = createCtrIvForAES(1, random);
Key key = createKeyForAES(256, random);
Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding", "BC");
String input = "input1234567";
cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
byte[] cipherText = cipher.doFinal(input.getBytes());
cipherText[9] ^= '0' ^ '9';
cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
byte[] plainText = cipher.doFinal(cipherText);
System.out.println("plain : " + new String(plainText));
}
public static SecretKey createKeyForAES(int bitLength, SecureRandom random)
throws NoSuchAlgorithmException, NoSuchProviderException {
KeyGenerator generator = KeyGenerator.getInstance("AES", "BC");
generator.init(128, random);
return generator.generateKey();
}
public static IvParameterSpec createCtrIvForAES(int messageNumber, SecureRandom random) {
byte[] ivBytes = new byte[16];
random.nextBytes(ivBytes);
ivBytes[0] = 1;
ivBytes[1] = 2;
ivBytes[2] = 3;
ivBytes[3] = 4;
for (int i = 0; i != 7; i++) {
ivBytes[8 + i] = 0;
}
ivBytes[15] = 1;
return new IvParameterSpec(ivBytes);
}
}
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