DeriveKey

Description: This function generates a cryptographic session key from a seed value.

Returns: Handle

Usage: Script

Format: DeriveKey(CSPHandle, AlgID, Seed [, Flags, Error])

Parameters: CSPHandle { handle } { required } { no default }
The handle of a CSP to use to generate the key.

AlgID { handle } { required } { no default }
Identifies the algorithm for which the key is to be generated. Values for this parameter vary depending on the CSP used, and are defined in WinCrypt.h

Seed { numeric } { required } { no default }
A text string to use as a seed.

Flags { numeric } { optional } { default: 0 }
An optional parameter specifying the flags to be passed to CryptGenKey. If omitted or invalid, then the value "0" is used.

Error { numeric } { optional } { no default }
An optional variable in which the error code for the function is returned. It has the following meaning:

Error	Meaning
0	Key successfully generated
1	CSPHandle or AlgID parameters invalid
X	Any other value is an error from CryptGenKey.

Comments: DeriveKey guarantees that when the same CSP and algorithms are used, the keys generated from the same seed are identical. The base data can be a password or any other user data. A handle to the key or key pair is returned. This handle can then be used as needed with any Crypto API function requiring a key handle. It is the VTS analog of the Crypto API CryptDeriveKey call.

The return value for this function is a handle to the Key. If an error occurs, then the return value is Invalid. A key has a value type of 37. If cast to text, then the hexadecimal value of the algorithm ID will be returned.

Example:

[

Key1;

Constant CALG_RC4 = 0x6801;

Constant KEY_SIZE = 40;

Constant Password = "A secret password";

]

Init [

If 1 Main;

[

{ Make a key }

Key1 = DeriveKey(CSP, CALG_RC4, Password, KEY_SIZE << 16);

]