Encryption issue using class CL_SEC_SXML_WRITER

[giancarla_aguilar]

We have to encrypt 1 field for sending to external API with AES256 algorithm with a provided AES256 key (from external system).  I used method CL_SEC_SXML_WRITER=>ENCRYPT for the encryption with algorithm parameter cl_sec_sxml_writer=>co_aes256_algorithm but I don't get the expected result.  I verify the result thru online encryption tools, and various tools results in the same encrypted value but not from CL_SEC_SXML_WRITER=>ENCRYPT.  I verified the hex values of the data and key and they are correct and consistent.  Every execution of the code, results to a different encrypted value.  The receiving system has also confirmed that they can not decrypt the passed value, same when I decrypt it thru online tools.  How can I make this method work?

Here is my code: 

DATA lv_aeskey TYPE string. "32 character key
    DATA lv_key TYPE xstring.
    DATA lv_data TYPE string.
    DATA lv_data_xstr TYPE string.
    DATA lv_msg TYPE xstring.

    data(lr_conv_key) = cl_abap_conv_out_ce=>create( ).
    lr_conv_key->write( data = lv_aeskey ).
    lv_key = lr_conv_key->get_buffer( ).

    "Converting the data - From string format to xstring. You can use any other method or function module which converts the string to xstring format
    data(lr_conv_data) = cl_abap_conv_out_ce=>create( ).
    lr_conv_data->write( data = lv_data ).
    lv_data_xstr = lr_conv_data->get_buffer( ).

    "Encrypt the data using the key
    cl_sec_sxml_writer=>encrypt(
      EXPORTING
        plaintext =  lv_data_xstr
        key       =  lv_key
        algorithm =  cl_sec_sxml_writer=>co_aes256_algorithm
      IMPORTING
        ciphertext = lv_msg ).