Decrypts a string that is encrypted with the Encrypt function.
decrypt(encrypted_string, key [, algorithm] [, encoding] [, ivorsalt] [, iterations]) → returns String
Name  Required  Default  Description 

encrypted_string  Yes  String to decrypt.  
key  Yes 
Key or seed used to encrypt the string. * For the CFMX_COMPAT algorithm, any combination of any number of characters; used as a seed used to generate a 32bit encryption key. * For all other algorithms, a key in the format used by the algorithm. For these algorithms, use the GenerateSecretKey function to generate the key. 

algorithm  No  CFMX_COMPAT 
The algorithm to use to decrypt the string. Must be the same as the algorithm used to encrypt the string. * CFMX_COMPAT: the algorithm used in ColdFusion MX 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) FIPS197. * BLOWFISH: the Blowfish algorithm defined by Bruce Schneier. * DES: the Data Encryption Standard algorithm defined by NIST FIPS463. * DESEDE: the "Triple DES" algorithm defined by NIST FIPS463.

encoding  No  UU 
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 AF and 09 represent the hexadecimal byte values. * UU: the UNIX standard UUEncode algorithm (default). If you specify this parameter, you must also specify the algorithm parameter.

ivorsalt  No 
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  No 
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. * For Password Based Encryption Algorithms: This is the binary Salt value to transform the password into a key. 
Generate an AES 128 bit key and then use it to encrypt and decrypt a secret.
ex={};
ex.key = generateSecretKey("AES");
ex.secret = "top secret";
ex.encrypted=encrypt(ex.secret, ex.key, "AES", "Base64");
ex.decrypted=decrypt(ex.encrypted, ex.key, "AES", "Base64");
writeDump(ex);