Applications that generate key get the randomness from the operating system. The operating system, in turn, gets the randomness where it can find it. Ideally the OS gets randomness from a proper hardware generator, which is present in modern PC and smartphone processors. Oct 29, 2010 I have also tested your code, and reproduced your issue. It seems that CryptCreateHash don’t support some algorithms on win7 such as CALGAES256. Then I changed the algorithm into CALGMD5, it can work well. So, you can switch to a different algorithm which is available on win7 to use. Here is the code which I have modified. Creating an encryption key from several other keys and using hash functions. Ask Question. There are better ways to generate a key. $endgroup$ – Ramhound May 2 '12 at 18:50. Instead of concatening the (sub)keys and then md5 the result. $endgroup$ – akira May 4 '12 at 5:53. Add a comment.
-->Important This API is deprecated. New and existing software should start using Cryptography Next Generation APIs. Microsoft may remove this API in future releases.
The CryptCreateHash function initiates the hashing of a stream of data. It creates and returns to the calling application a handle to a cryptographic service provider (CSP) hash object. This handle is used in subsequent calls to CryptHashData and CryptHashSessionKey to hash session keys and other streams of data.Syntax
Parameters
hProv
A handle to a CSP created by a call toCryptAcquireContext.
Algid
An ALG_ID value that identifies the hash algorithm to use.
Valid values for this parameter vary, depending on the CSP that is used. For a list of default algorithms, see Remarks.
hKey
If the type of hash algorithm is a keyed hash, such as the Hash-Based Message Authentication Code (HMAC) or Message Authentication Code (MAC) algorithm, the key for the hash is passed in this parameter. For nonkeyed algorithms, this parameter must be set to zero.
For keyed algorithms, the key must be to a block cipher key, such as RC2, that has a cipher mode of Cipher Block Chaining (CBC).
dwFlags
The following flag value is defined.
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Value | Meaning |
---|---|
| This flag is not used. |
phHash
The address to which the function copies a handle to the new hash object. When you have finished using the hash object, release the handle by calling the CryptDestroyHash function.
Return value
If the function succeeds, the function returns TRUE.
If the function fails, it returns FALSE. For extended error information, callGetLastError.
The error codes prefaced by NTE are generated by the particular CSP you are using. The following table shows some of the possible error codes.
Return code | Description |
---|---|
| One of the parameters specifies a handle that is not valid. |
| One of the parameters contains a value that is not valid. This is most often a pointer that is not valid. |
| The operating system ran out of memory during the operation. |
| The Algid parameter specifies an algorithm that this CSP does not support. |
| The dwFlags parameter is nonzero. |
| A keyed hash algorithm, such as CALG_MAC, is specified by Algid, and the hKey parameter is either zero or it specifies a key handle that is not valid. This error code is also returned if the key is to a stream cipher or if the cipher mode is anything other than CBC. |
| The CSP ran out of memory during the operation. |
Remarks
For a list of Microsoft service providers and the algorithms they implement, see Microsoft Cryptographic Service Providers.
The computation of the actual hash is done with theCryptHashData andCryptHashSessionKey functions. These require a handle to the hash object. After all the data has been added to the hash object, any of the following operations can be performed:
- The hash value can be retrieved by using CryptGetHashParam.
- A session key can be derived by using CryptDeriveKey.
- The hash can be signed by using CryptSignHash.
- A signature can be verified by using CryptVerifySignature.
Examples
Windows Default Key Generation Algorithm Calg Md5 File
The following example shows initiating the hashing of a stream of data. It creates and returns to the calling application a handle to a hash object. This handle is used in subsequent calls toCryptHashData andCryptHashSessionKey to hash any stream of data. For an example that includes the complete context for this example, seeExample C Program: Creating and Hashing a Session Key.For another example that uses this function, see Example C Program: Signing a Hash and Verifying the Hash Signature.
Windows Default Key Generation Algorithm Calg Md5 Free
Requirements
Minimum supported client | Windows XP [desktop apps only] |
Minimum supported server | Windows Server 2003 [desktop apps only] |
Target Platform | Windows |
Header | wincrypt.h |
Library | Advapi32.lib |
DLL | Advapi32.dll |
See also
-->The following example creates and hashes a session key that can be used to encrypt a message, text, or file.
Key Generation Software
This example also shows using the following CryptoAPI functions:
Windows Default Key Generation Algorithm Calg Md5 Code
- CryptAcquireContext to acquire a cryptographic service provider.
- CryptCreateHash to create an empty hash object.
- CryptGenKey to create a random session key.
- CryptHashSessionKey to hash the session key created.
- CryptDestroyHash to destroy the hash.
- CryptDestroyKey to destroy the key created.
- CryptReleaseContext to release the CSP.
Free Key Generation Software
This example uses the function MyHandleError. The code for this function is included with the sample. Code for this and other auxiliary functions is also listed under General Purpose Functions.