Question ID : 138
Created on 2010-07-21 at 12:12 PM
Author : Veryant Support [support@veryant.com]
Online URL : http://support.veryant.com/support/phpkb/question.php?ID=138
Question:
Where can I find more information on A$ENCRYPT and A$DECRYPT? I am getting errors involving 'padding' and 'multiple of 8 bytes' when I use these routines.Answer:
The size of the key passed to A$ENCRYPT or A$DECRYPT must be less than or equal to 128-bits (i.e. 16 bytes). For example, use the following data item for your encryption key:
77 encryption-key pic x(16).
When A$ENCRYPT returns, the length of the encrypted-data is set to an exact value, and in A$DECRYPT the length of data-to-decrypt must be exact. Use items defined as PIC X ANY LENGTH to ensure that you can retrieve and set the lengths precisely. For example, use the following data items for your encrypted-data and data-to-decrypt:
77 encrypted-data pic x any length.
77 data-to-decrypt pic x any length.
Then, for example, you can take the output from A$ENCRYPT (i.e. encrypted-data) and pass it as the input to A$DECRYPT (i.e. data-to-decrypt) to reverse the encryption.
See the attached sample program, encryption.cbl
Note that the encrypted data is binary and is not an encoded character string.
The A$ENCRYPT routine does the equivalent of the following Java code:
public final static String CRYPT_ALGORITHM = "Blowfish";
Cipher cipher = Cipher.getInstance(CRYPT_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(encryptionKey, 0, encryptionKey.length, CRYPT_ALGORITHM));
byte[] encryptedData = cipher.doFinal(dataToEncrypt, 0, dataToEncrypt.length));
The A$DECRYPT routine does the equivalent of the following Java code:
public final static String CRYPT_ALGORITHM = "Blowfish";
Cipher cipher = Cipher.getInstance(CRYPT_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(encryptionKey, 0, encryptionKey.length, CRYPT_ALGORITHM));
byte[] decryptedData = cipher.doFinal(dataToDecrypt, 0, dataToDecrypt.length));
where dataToDecrypt, encryptionKey and decryptedData are the 3 parameters passed to A$DECRYPT.
PKCS5Padding is the default padding scheme for Blowfish ciphers.
Detailed information can be found in the Java Cryptography Architecture (JCA) Reference Guide here.