Hash

Description

Converts a variable-length string to a fixed-length string that can act as a “fingerprint” or unique identifier for the original string. It is not possible to convert the hash result back to the source string.

Returns

A string.

Category

Conversion functions, Security functions, String functions

Function syntax

Hash(string [, algorithm [, encoding ]])

History

ColdFusion MX 7: Added the algorithm and encoding parameters.

Parameters

Parameter

Description

string

String to hash.

algorithm

(Optional) The algorithm to use to hash the string. ColdFusion installs a cryptography library with the following algorithms:

  • CFMX_COMPAT: Generates a hash string identical to that generated by ColdFusion MX and ColdFusion MX 6.1 (default).

  • MD5: (default) Generates a 32-character, hexadecimal string, using the MD5 algorithm (The algorithm used in ColdFusion MX and prior releases).

  • SHA: Generates a 28-character string using the Secure Hash Standard SHA-1 algorithm specified by Nation Institute of Standards and Technology (NIST) FIPS-180-2.

  • SHA-256: Generates a 44-character string using the SHA-256 algorithm specified by FIPS-180-2.

  • SHA-384: Generates a 64-character string using the SHA-384 algorithm specified by FIPS-180-2.

  • SHA-512: Generates an 88-character string using the SHA-1 algorithm specified by FIPS-180-2.

The Enterprise Edition of ColdFusion installs the RSA BSafe Crypto-J library, which provides FIPS-140 Compliant Strong Cryptography. It includes the following algorithms:

  • MD2: The MD2 hash algorithm defined by RFC 1319.

  • MD5: The defined by RFC 1321.

  • RIPEMD160: RACE Integrity Primitives Evaluation Message Digest 160-bit message digest algorithm and cryptographic hash function.

  • SHA-1: The 160-bit secure hash algorithm defined by FIPS 180-2 and FIPS 198.

  • SHA-224: The 224-bit secure hash algorithm defined by FIPS 180-2 and FIPS 198.

  • SHA-256: The 256-bit secure hash algorithm defined by FIPS 180-2 and FIPS 198.

  • SHA-384: The 384-bit secure hash algorithm defined by FIPS 180-2 and FIPS 198.

  • SHA-512: The 512-bit secure hash algorithm defined by FIPS 180-2 and FIPS 198.

If you install a security provider with additional cryptography algorithms, you can also specify any of its hashing algorithms.

encoding

(Optional; to use this attribute, also specify the algorithm parameter) A string specifying the encoding to use when converting the string to byte data used by the hash algorithm. Must be a character encoding name recognized by the Java runtime. The default value is the value specified by the defaultCharset entry in the neo-runtime.xml file, which is normally UTF-8. Ignored when using the CFMX_COMPAT algorithm.

Usage

The result of this function is useful for comparison and validation. For example, you can store the hash of a password in a database without exposing the password. You can check the validity of the password by hashing the entered password and comparing the result with the hashed password in the database.

ColdFusion uses the Java Cryptography Extension (JCE) and installs a Sun Java 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, Adobe cannot provide technical support for third-party security providers.

The encoding attribute is normally not required. It provides a mechanism for generating identical hash values on systems with different default encodings. ColdFusion uses a default encoding of UTF-8 unless you modify the defaultCharset entry in the neo-runtime.xml file.

Example

The following example lets you enter a password and compares the hashed password with a hash value saved in the SecureData table of the cfdocexamples database. This table has the following entries:

User ID

Password

blaw

blaw

dknob

dknob

 
<h3>Hash Example</h3> 
 
<!--- Do the following if the form is submitted. ---> 
<cfif IsDefined("Form.UserID")> 
 
    <!--- query the data base. --->  
    <cfquery name = "CheckPerson" datasource = "cfdocexamples"> 
        SELECT PasswordHash 
        FROM SecureData 
        WHERE UserID = <cfqueryparam value = "#Form.userID#" 
            cfsqltype = 'CF_SQL_VARCHAR'>  
    </cfquery> 
 
    <!--- Compare query PasswordHash field and the hashed form password 
            and display the results. ---> 
    <cfoutput> 
        <cfif Hash(Form.password, "SHA") is not checkperson.passwordHash> 
            User ID #Form.userID# or password is not valid. Try again. 
        <cfelse> 
            Password is valid for User ID #Form.userID#. 
        </cfif> 
    </cfoutput> 
</cfif> 
 
<!--- Form for entering ID and password. ---> 
<form action="#CGI.SCRIPT_NAME#" method="post"> 
    <b>User ID: </b> 
    <input type = "text" name="UserID" ><br> 
    <b>Password: </b> 
    <input type = "text" name="password" ><br><br> 
    <input type = "Submit" value = "Encrypt my String"> 
</form>