Encoding, encryption and hashing are about data transformation. While encoding and encryption are reversible (given the output and some additional information, the input can be obtained), hashing is a one way, irreversible. change.
processing purpose
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Encoding: data + algorithm => for transfer and consumation purposes
Encryption: data + algorithm + secret key => for secure transfer
Hashing: data + hash function => for data integrity, for sender identification, fast search for a data record, building caches
Encoding uses a publicly available algorithm and a reverse process can be used to get at the original data. Its purpose is to provide a format that allows data to be transferred and consumed by a different system. It does not solve security issues. Examples are base64, unicode, URL/HTML encoding etc.
(pack creates a string concatenated from 4 unsigned chars/octets (in machine form) of the IP address. unpack transforms this string into an unsigned long (32 bit) in "network" (big endian) order.)
B)
Base64 encoding (radix-64 representation) is widely used to represent binary data in text format, used for data transport.
CGI script:
While an encrypted message can be decrypted to provide the original plain text, decryption can only be carried out by those who know a key, that was used together with a particular algorithm during the encryption. Encrypted data can be, therefore, securely transferred to the desired recipient.
Hashing transforms an arbitrary string of characters into a fixed-length string through the use of a hash function. The resulting hash value/hash sum/hash/message digest should be be always the same for the same input, and it is should be practically impossible, ie computationally infeasible, to invert/find the original value from the hash. A hashing function should never produce the same hash for two different inputs. Hashing is used for checking data integrity, sender's identity etc.
Perl modules:
processing purpose
------------------------------------------------------------------------------------------------------------
Encoding: data + algorithm => for transfer and consumation purposes
Encryption: data + algorithm + secret key => for secure transfer
Hashing: data + hash function => for data integrity, for sender identification, fast search for a data record, building caches
Encoding
Encoding uses a publicly available algorithm and a reverse process can be used to get at the original data. Its purpose is to provide a format that allows data to be transferred and consumed by a different system. It does not solve security issues. Examples are base64, unicode, URL/HTML encoding etc.
Example:
A)my $ip = '192.168.2.100'; my $ip_encoded = unpack('N', pack('C4', split(/\D/, $ip, 4)));
(pack creates a string concatenated from 4 unsigned chars/octets (in machine form) of the IP address. unpack transforms this string into an unsigned long (32 bit) in "network" (big endian) order.)
B)
Base64 encoding (radix-64 representation) is widely used to represent binary data in text format, used for data transport.
CGI script:
use strict; use warnings; use CGI; use JSON; use MIME::Base64; my $cgi = CGI->new(); my $image_file = "/var/www/images/sunflower.jpg"; undef $/; open my $fhandle, '<', $image_file; my $image = <$fhandle>; $image_encoded = encode_base64($image); my $response = to_json({ photo => $image_encoded }); print $cgi->header(-Content_type => 'application/json'); print $response;
Then on the web page:
<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Encode64 Example</title> <script src="jquery-1.2.1.min.js" type="text/javascript" charset="utf-8"></script> </head> <body> <p>Encode64 Example</p> <script> $(document).ready(function () { $.getJSON('/test_my_app', function(data) { var photo = data.photo; // contains the encoded contents of the image var elems = []; elems.push('<table>'); elems.push('<tr>'); elems.push('<td id="photo">' + '<img src="data:image/jpg;base64, ' + photo + '" />' + '</td>'); elems.push('</tr>'); elems.push('</table>'); $('body').append(elems.join('')); }); }); </script> </body> </html>
Encryption
While an encrypted message can be decrypted to provide the original plain text, decryption can only be carried out by those who know a key, that was used together with a particular algorithm during the encryption. Encrypted data can be, therefore, securely transferred to the desired recipient.
Example
use strict; use warnings; use utf8; use v5.018; use Crypt::CBC; my $plaintext = "World's biggest secret"; my $cipher = Crypt::CBC->new( -key => 'my_secret_key', -cipher => 'Blowfish', ); my $ciphertext = $cipher->encrypt($plaintext); $plaintext = $cipher->decrypt($ciphertext); say "$plaintext";
Hashing
Hashing transforms an arbitrary string of characters into a fixed-length string through the use of a hash function. The resulting hash value/hash sum/hash/message digest should be be always the same for the same input, and it is should be practically impossible, ie computationally infeasible, to invert/find the original value from the hash. A hashing function should never produce the same hash for two different inputs. Hashing is used for checking data integrity, sender's identity etc.
Perl modules:
Digest::SHA
Crypt::PBKDF2 etc
Examples
use Digest::SHA qw(sha256_hex); $data = "this is top secret"; $digest = sha256_hex($data);
use Crypt::PBKDF2; my $pbkdf2 = Crypt::PBKDF2->new( hash_class => 'HMACSHA1' # default, other functions available iterations => 120000, output_len => 25, salt_len => 4, ); my $hash = $pbkdf2->generate("my_biggest_secret"); # store in database # later on, somebody logs in # retrieve the person's hash from the database # check the password if ($pbkdf2->validate($hash, $password)) { .... }
