Re: Regarding Decryption of AES128 encrypted data in RPGLE and query regarding CRC 32 [PRIVATE REPLY]

[Peter Dow <petercdow@xxxxxxxxx>]

Hi Rishi,

I went to the website you mentioned, 
https://www.devglan.com/online-tools/aes-encryption-decryption, and 
tried decrypting

u3VtNgfyWU9faZc3Iaa8ZWbE5UZCfmC17yA4MyW0ghflt9dNQNDpCcgMZiG/kXPE4vv2CHL93B4iKiODHxxdVA==

with password (secret key)

6-9d15-ec98bcc81ec4275OIM1TS7LI

and I noticed a couple of things.

1. Since the encryption is AES128, the password length must be 16 
bytes.  The pswd in your program is 31 bytes.

2. The "encrypted" data is actually base64 encoded.  In order to decrypt 
it in RPG, you would first have to decode it from base64, then decrypt it.


On top of that, when I used the aforementioned website to encrypt 
'whatever text', in AES with 128-bit key, mode ECB, and password 
'mypasswordis16xy', the encrypted value is

 x'831720A57F742CBB3A86AB24A3AA23AE'.

If I use the SQL encrypt_AES function, with the same password, the 
encrypted value is

x'4CB947FF0025D5A6B96180506FFE4F23B96180506FFE4F23'.

The reason for this difference probably has something to do with the 
following notes from IBM's SQL manual on the encrypt_AES function:

"The length attribute of the result depends on the arguments that are 
specified:
 * when /password-string/ is specified but a /hint-string/ is not 
specified, the length
     attribute of /data-string/ plus 24 plus the number of bytes to a 
16-byte boundary.
 * Otherwise, the length attribute of /data-string/ plus 64 plus the 
number of bytes to
    a 16-byte boundary."

Apparently IBM's encrypt_AES function includes more than just the 
encrypted value in its result.

In short, it looks like you cannot use IBM's decrypt_AES function to 
decrypt a value encrypted by anything other than IBM's encrypt_AES function.

--
*Peter Dow* /
Dow Software Services, Inc.
909 793-9050
petercdow@xxxxxxxxx <mailto:petercdow@xxxxxxxxx>
pdow@xxxxxxxxxxxxxx <mailto:pdow@xxxxxxxxxxxxxx>

/
On 9/30/2019 4:50 AM, Rishi Seth wrote:
> I Know below is the IBM API for same but need a real working example which
> could decrypt data which is encoded using UTF8 or ACII. with 128 bit key
> and Mode is ECB?



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