Image::ExifTool::AES(3pm)

1Image::ExifTool::AES(3)User Contributed Perl DocumentatioInmage::ExifTool::AES(3)
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NAME

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

9         use Image::ExifTool::AES qw(Crypt);
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11         $err = Crypt(\$plaintext, $key, 1);   # encryption
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13         $err = Crypt(\$ciphertext, $key);     # decryption
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DESCRIPTION

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

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

25   Crypt
26       Implement AES encryption/decryption with cipher-block chaining.
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28       Inputs:
29           0) Scalar reference for data to encrypt/decrypt.
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31           1) Encryption key string (must have length 16, 24 or 32).
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33           2) [optional] Encrypt flag (false to decrypt).
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35           3) [optional] Flag to avoid removing padding after decrypting, or
36           to avoid adding 16 bytes of padding before encrypting when data
37           length is already a multiple of 16 bytes.
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39       Returns:
40           On success, the return value is undefined and the data is encrypted
41           or decrypted as specified.  Otherwise returns an error string and
42           the data is left in an indeterminate state.
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44       Notes:
45           The length of the encryption key dictates the AES mode, with
46           lengths of 16, 24 and 32 bytes resulting in AES-128, AES-192 and
47           AES-256.
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49           When encrypting, the input data may be any length and will be
50           padded to an even 16-byte block size using the specified padding
51           technique.  If the encrypt flag has length 16, it is used as the
52           initialization vector for the cipher-block chaining, otherwise a
53           random IV is generated.  Upon successful return the data will be
54           encrypted, with the first 16 bytes of the data being the CBC IV.
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56           When decrypting, the input data begins with the 16-byte CBC
57           initialization vector.
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BUGS

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

65       Copyright 2003-2021, Phil Harvey (philharvey66 at gmail.com)
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67       This library is free software; you can redistribute it and/or modify it
68       under the same terms as Perl itself.
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REFERENCES

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