Invalid block size. An exception. Input length must be a multiple of 16 when decrypting with additional encryption

Question

In my application, I encrypt and decrypt data using secretKey. For this, I use the AES algorithm. But I get an exception in the decryption, one value out of the three already encrypted values ​​using the secret key.

An exception:

Illegal Block Size Exception Input length must be multiple of 16 when decrypting with padded cipher. 

Below is my code:

Function for encyrpt value

 public static String symmetricEncrypt(String text, String secretKey) { BASE64Decoder decoder = new BASE64Decoder(); byte[] raw; String encryptedString; SecretKeySpec skeySpec; BASE64Encoder bASE64Encoder = new BASE64Encoder(); byte[] encryptText = text.getBytes(); Cipher cipher; try { raw = decoder.decodeBuffer(secretKey); skeySpec = new SecretKeySpec(raw, "AES"); cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); encryptedString = bASE64Encoder.encode(cipher.doFinal(encryptText)); } catch (Exception e) { e.printStackTrace(); return "Error"; } return encryptedString; } 

Value decryption function

 public static String symmetricDecrypt(String text, String secretKey) { BASE64Decoder decoder = new BASE64Decoder(); BASE64Decoder base64Decoder = new BASE64Decoder(); Cipher cipher; String encryptedString; byte[] encryptText = null; byte[] raw; SecretKeySpec skeySpec; try { raw = decoder.decodeBuffer(secretKey); skeySpec = new SecretKeySpec(raw, "AES"); encryptText = base64Decoder.decodeBuffer(text); cipher = Cipher.getInstance("AES"); cipher.init(Cipher.DECRYPT_MODE, skeySpec); encryptedString = new String(cipher.doFinal(encryptText)); } catch (Exception e) { e.printStackTrace(); return "Error"; } return encryptedString; } 

Below are the values ​​that I encrypt and decrypt

 String secretKey = "XMzDdG4D03CKm2IxIWQw7g=="; String value1= "ABCD"; String enctypedValue1= "3uweh4pzoVyH1uODQmVNJA=="; String enctypedValue2= "37PTC20w4DMZYjG3f+GWepSvAbEJUccMXwS/lXilLav1qM/PrCTdontw5/82OdC1zzyhDEsFVRGo rV6gXAQcm+Zai15hliiUQ8l8KRMtUl4="; String value4= "20000"; /** Ecnryption and decryption of value1 **/ String encryptedValue1= symmetricEncrypt(value1, secretKey); String decryptedValue1 = symmetricDecrypt(encryptedValue1, secretKey); /** Decryption of enctypedValue1 **/ String decryptedValue2 = symmetricDecrypt(enctypedValue1, secretKey); System.out.println(decryptedValue2); /** Decryption of enctypedValue2 (Not decrypted)**/ String decryptedValue3 = symmetricDecrypt(enctypedValue2, secretKey); System.out.println(decryptedValue3); /** Ecnryption and decryption of value4 **/ String encryptedValue4= symmetricEncrypt(value4, secretKey); String decryptedValue4 = symmetricDecrypt(encryptedValue4, secretKey); 

In the test function, I wrote the following three test cases.

• The new value (value1) is encrypted and decrypted using the private key.
• Two examples of encrypted values ​​(enctypedValue1, enctypedValue2) that are decrypted using the same secret key. encryptedValue2, which received a problem decrypting using the same secret key.
• The new value (value 4) is encrypted and decrypted using the secret key.

When decrypting encryptedValue2, I get the following exception:

 Illegal Block Size Exception Input length must be multiple of 16 when decrypting with padded cipher 

Here is what I got so far.

• The problem value seems to have a problem when decoding, it returns an 81 array of length that cannot be decrypted?

• If this problem should happen, it should have happened with all the meanings.

• Is this a value-specific issue, or is it related to the add-on, or may it have different behavior in different browsers, different os?

Answer 1

I managed to run the code without any problems. However, I used Apache Base64 for encoding / decoding ... maybe your Base64 has errors. If you wrote it yourself, there is a big chance that you missed some cases. For real production code, use heavily tested libraries such as Apache.

You can find the library that I used for Base64 here: http://commons.apache.org/proper/commons-codec/download_codec.cgi

Here is the full working code:

  package security.symmatric; import javax.crypto.Cipher; import javax.crypto.spec.SecretKeySpec; import org.apache.commons.codec.binary.Base64; public class AES { public static String symmetricEncrypt(String text, String secretKey) { byte[] raw; String encryptedString; SecretKeySpec skeySpec; byte[] encryptText = text.getBytes(); Cipher cipher; try { raw = Base64.decodeBase64(secretKey); skeySpec = new SecretKeySpec(raw, "AES"); cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); encryptedString = Base64.encodeBase64String(cipher.doFinal(encryptText)); } catch (Exception e) { e.printStackTrace(); return "Error"; } return encryptedString; } public static String symmetricDecrypt(String text, String secretKey) { Cipher cipher; String encryptedString; byte[] encryptText = null; byte[] raw; SecretKeySpec skeySpec; try { raw = Base64.decodeBase64(secretKey); skeySpec = new SecretKeySpec(raw, "AES"); encryptText = Base64.decodeBase64(text); cipher = Cipher.getInstance("AES"); cipher.init(Cipher.DECRYPT_MODE, skeySpec); encryptedString = new String(cipher.doFinal(encryptText)); } catch (Exception e) { e.printStackTrace(); return "Error"; } return encryptedString; } public static void main(String[] args) { String secretKey = "XMzDdG4D03CKm2IxIWQw7g=="; String value1= "ABCD"; String enctypedValue1= "3uweh4pzoVyH1uODQmVNJA=="; String enctypedValue2= "37PTC20w4DMZYjG3f+GWepSvAbEJUccMXwS/lXilLav1qM/PrCTdontw5/82OdC1zzyhDEsFVRGo rV6gXAQcm+Zai15hliiUQ8l8KRMtUl4="; String value4= "20000"; /** Ecnryption and decryption of value1 **/ String encryptedValue1= symmetricEncrypt(value1, secretKey); String decryptedValue1 = symmetricDecrypt(encryptedValue1, secretKey); System.out.println(decryptedValue1); /** Decryption of enctypedValue1 **/ String decryptedValue2 = symmetricDecrypt(enctypedValue1, secretKey); System.out.println(decryptedValue2); /** Decryption of enctypedValue2 **/ String decryptedValue3 = symmetricDecrypt(enctypedValue2, secretKey); System.out.println(decryptedValue3); /** Ecnryption and decryption of value4 **/ String encryptedValue4= symmetricEncrypt(value4, secretKey); String decryptedValue4 = symmetricDecrypt(encryptedValue4, secretKey); System.out.println(decryptedValue4); } }