Adobe ColdFusion 8

Decrypt

Description

Decrypts a string that is encrypted using a standard encryption technique, including strings encrypted by the Encrypt function.

Returns

An unencrypted string.

Category

Security functions, String functions

Function syntax

Decrypt(encrypted_string, key[, algorithm, encoding, IVorSalt, iterations])

See also

Duplicate, Encrypt

History

ColdFusion 8: Added support for encryption using the RSA BSafe Crypto-J library on Enterprise Edition.

ColdFusion MX 7.01: Added the IVorSalt and iterations parameters.

ColdFusion MX 7: Added the algorithm and encoding parameters.

Parameters

Parameter

Description
encrypted_string

String to decrypt.
key

String. For the CFMX_COMPAT algorithm, the seed that was used to encrypt the string; for all other algorithms, the string generated by the generateSecretKey() method.
algorithm

(Optional) The Enterprise Edition of ColdFusion installs the RSA BSafe Crypto-J library, which provides FIPS-140 Compliant Strong Cryptography. For a list of algorithms, see the Encrypt function.

The Standard Edition of ColdFusion installs a cryptography library with the following algorithms:

  • CFMX_COMPAT: the algorithm used in ColdFusion MX 7 and prior releases. This algorithm is the least secure option (default).
  • AES: the Advanced Encryption Standard specified by the National Institute of Standards and Technology (NIST) FIPS-197.
  • BLOWFISH: the Blowfish algorithm defined by Bruce Schneier.
  • DES: the Data Encryption Standard algorithm defined by NIST FIPS-46-3.
  • DESEDE: the "Triple DES" algorithm defined by NIST FIPS-46-3.

If you install a security provider with additional cryptography algorithms, you can also specify any of its string encryption and decryption algorithms.
encoding

(Optional; if you specify this parameter, you must also specify the algorithm parameter.) The binary encoding used to represent the data as a string. Must be the same as the algorithm used to encrypt the string.

  • Base64: the Base64 algorithm, as specified by IETF RFC 2045.
  • Hex: the characters A-F and 0-9 represent the hexadecimal byte values.
  • UU: the UNIX standard UUEncode algorithm (default).
IVorSalt

(Optional) Specify this parameter to adjust ColdFusion encryption to match the details of other encryption software. If you specify this parameter, you must also specify the algorithm parameter.

  • For Block Encryption Algorithms: This is the binary Initialization Vector value to use with the algorithm. The algorithm must contain a Feedback Mode other than ECB. This must be a binary value that is exactly the same size as the algorithm block size.
  • For Password Based Encryption Algorithms: This is the binary Salt value to transform the password into a key.
iterations

(Optional) The number of iterations to transform the password into a binary key. Specify this parameter to adjust ColdFusion encryption to match the details of other encryption software. If you specify this parameter, you must also specify the algorithm parameter with a Password Based Encryption (PBE) algorithm. Do not specify this parameter for Block Encryption Algorithms. You must use the same value to encrypt and decrypt the data.

Usage

This function uses a symmetric key-based algorithm, in which the same key is used to encrypt and decrypt a string. The parameter values must match the values used to encode string. The security of the encrypted string depends on maintaining the secrecy of the key.

ColdFusion uses the Java Cryptography Extension (JCE) and installs a Sun Java 1.4.2 runtime that includes the Sun JCE default security provider. This provider includes the algorithms listed in the Parameters section. The JCE framework includes facilities for using other provider implementations; however, cannot provide technical support for third-party security providers.

Example

<h3>Decrypt Example</h3>

<!--- Do the following if the form has been submitted. --->
<cfif IsDefined("Form.myString")>
    <cfscript>
        /* GenerateSecretKey does not generate key for the CFMX_COMPAT algorithm,
        so use the key from the form.
        */
        if (Form.myAlgorithm EQ "CFMX_COMPAT")
            theKey=Form.MyKey;
        // For all other encryption techniques, generate a secret key.
        else
            theKey=generateSecretKey(Form.myAlgorithm);
        //Encrypt the string
        encrypted=encrypt(Form.myString, theKey, Form.myAlgorithm,
            Form.myEncoding);
        //Decrypt it
        decrypted=decrypt(encrypted, theKey, Form.myAlgorithm, Form.myEncoding);
    </cfscript>

    <!--- Display the values used for encryption and decryption, 
            and the results. --->
    <cfoutput>
        <b>The algorithm:</b> #Form.myAlgorithm#<br>
        <b>The key:</B> #theKey#<br>
        <br>
        <b>The string:</b> #Form.myString# <br>
        <br>
        <b>Encrypted:</b> #encrypted#<br>
        <br>
        <b>Decrypted:</b> #decrypted#<br>
    </cfoutput>
</cfif>

<!--- The input form.--->
<form action="#CGI.SCRIPT_NAME#" method="post">
    <b>Select the encoding</b><br>
    <select size="1" name="myEncoding">
        <option selected>UU</option>
        <option>Base64</option>
        <option>Hex</option>
    </select><br>
    <br>
    <b>Select the algorithm</b><br>
    <select size="1" name="myAlgorithm">
        <option selected>CFMX_COMPAT</option>
        <option>AES</option>
        <option>DES</option>
        <option>DESEDE</option>
    </select><br>
    <br>
    <b>Input your key</b> (used for CFMX_COMPAT encryption only)<br>
    <input type = "Text" name = "myKey" value = "MyKey"><br>
    <br>
    <b>Enter string to encrypt</b><br>
    <textArea name = "myString" cols = "40" rows = "5" WRAP = "VIRTUAL">
        This string will be encrypted (you can replace it with more typing).
    </textArea><br>
    <input type = "Submit" value = "Encrypt my String">
</form>