Created
April 2, 2009 22:40
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algorithm based on base64 for general proposes
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<?php | |
function codificar($valor, $chave){ | |
if (($chave = codificacao_chave($chave)) !== false){ | |
list($inicio, $fim) = $chave; | |
} else { | |
return false; | |
} | |
$base = base64_encode($valor); | |
$base = str_replace('=', '', $base); | |
$base = strrev($base); | |
$md5 = md5($valor); | |
$base = (substr($md5, 0, $inicio) . $base . substr($md5, -$fim)); | |
return $base; | |
} | |
function decodificar($valor, $chave){ | |
if (($chave = codificacao_chave($chave)) !== false){ | |
list($inicio, $fim) = $chave; | |
} else { | |
return false; | |
} | |
$hash = (substr($valor, 0, $inicio) . substr($valor, -$fim)); | |
$base = substr($valor, 0, -$fim); | |
$base = substr($base, $inicio); | |
$base = strrev($base); | |
$cmp = (strlen($base) % 4); | |
if ($cmp > 0) $base .= str_repeat('=', $cmp); | |
$base = base64_decode($base); | |
$md5 = md5($base); | |
$md5 = (substr($md5, 0, $inicio) . substr($md5, -$fim)); | |
return (($md5 == $hash) ? $base : false); | |
} | |
function codificacao_chave($chave){ | |
$valor = md5($chave); | |
$t = strlen($valor); | |
$dig1 = ''; | |
$dig2 = ''; | |
for ($i = 0; $i < $t; $i++){ | |
$ch = substr($valor, $i, 1); | |
if (is_numeric($ch) && ($ch !== '0')){ | |
if ($dig1 == ''){ | |
$dig1 = $ch; | |
} elseif ($dig2 == ''){ | |
$dig2 = $ch; | |
} else { | |
break; | |
} | |
} | |
} | |
return (($dig1 != '') && ($dig2 != '')) ? array($dig1, $dig2) : false; | |
} | |
?> |
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