NAME

       Image::ExifTool::AES - AES encryption with cipher-block chaining

SYNOPSIS

         use Image::ExifTool::AES qw(Crypt);

         $err = Crypt(\$plaintext, $key, 1);   # encryption

         $err = Crypt(\$ciphertext, $key);     # decryption

DESCRIPTION

       This module contains an implementation of the AES encryption/decryption algorithms with cipher-block
       chaining (CBC) and RFC 2898 PKCS #5 padding.  This is the AESV2 and AESV3 encryption mode used in PDF
       documents.

EXPORTS

       Exports nothing by default, but "Crypt" may be exported.

METHODS

   Crypt
       Implement AES encryption/decryption with cipher-block chaining.

       Inputs:
           0) Scalar reference for data to encrypt/decrypt.

           1) Encryption key string (must have length 16, 24 or 32).

           2) [optional] Encrypt flag (false to decrypt).

           3) [optional] Flag to avoid removing padding after decrypting, or to avoid adding 16 bytes of padding
           before encrypting when data length is already a multiple of 16 bytes.

       Returns:
           On  success,  the  return  value  is  undefined  and the data is encrypted or decrypted as specified.
           Otherwise returns an error string and the data is left in an indeterminate state.

       Notes:
           The length of the encryption key dictates the AES mode, with lengths of 16, 24 and 32 bytes resulting
           in AES-128, AES-192 and AES-256.

           When encrypting, the input data may be any length and will be padded to an even  16-byte  block  size
           using  the  specified  padding  technique.   If  the  encrypt  flag  has length 16, it is used as the
           initialization vector for the cipher-block chaining,  otherwise  a  random  IV  is  generated.   Upon
           successful return the data will be encrypted, with the first 16 bytes of the data being the CBC IV.

           When decrypting, the input data begins with the 16-byte CBC initialization vector.

BUGS

       This  code  is blindingly slow.  But in truth, slowing down processing is the main purpose of encryption,
       so this really can't be considered a bug.

AUTHOR

       Copyright 2003-2024, Phil Harvey (philharvey66 at gmail.com)

       This library is free software; you can redistribute it and/or modify it under  the  same  terms  as  Perl
       itself.

REFERENCES

       <http://www.hoozi.com/Articles/AESEncryption.htm>
       <http://www.csrc.nist.gov/publications/fips/fips197/fips-197.pdf>
       <http://www.faqs.org/rfcs/rfc3602.html>

SEE ALSO

       Image::ExifTool(3pm)

perl v5.38.2                                       2024-02-03                          Image::ExifTool::AES(3pm)