CryptAcquireContext info  Overview  Group

The CryptAcquireContext function is used to acquire a handle to a particular key container within a particular CSP. This returned handle can then be used to make calls to the selected CSP.

This function performs two operations. It first attempts to find a CSP with the characteristics described in the dwProvType and pszProvider parameters. If the CSP is found, then the function attempts to find a key container within the CSP matching the name specified by the pszContainer parameter.

This function can also be used to create and destroy key containers, depending on the value of the dwFlags parameter.

BOOL CRYPTFUNC CryptAcquireContext(

Parameters

phProv

[out] The address to which the function copies a handle to the CSP.

pszContainer

[in] The key container name. This is a zero-terminated string that identifies the key container to the CSP. This name is independent of the method used to store the keys. Some CSPs will store their key containers internally (in hardware), some will use the system Registry, and others will use the file system.

If this parameter is NULL, then a default key container name will be used. For example, if the Microsoft RSA Base Provider is being used, then the current user’s logon name will be used as the name of the key container. Other CSPs may also have default key containers that can be acquired in this way.

An application can obtain the name of the acquired key container at a later time by reading the PP_CONTAINER parameter from the CryptGetProvParam function.

pszProvider

[in] The provider name. This is a zero-terminated string that specifies the CSP to be used.

If this parameter is NULL then the user default provider is used. This situation is discussed in detail in the section Interfacing with a Cryptographic Service Provider (CSP).

An application can obtain the name of the acquired CSP at a later time by reading the PP_NAME parameter from the CryptGetProvParam function.

dwProvType

[in] The type of provider to acquire. The following provider types are predefined. These are discussed in detail in the section Interfacing with a Cryptographic Service Provider (CSP).

• PROV_RSA_FULL

• PROV_RSA_SIG

• PROV_DSS

• PROV_FORTEZZA

• PROV_MS_MAIL

dwFlags

[in] The flag values. This parameter is normally set to zero, but some applications will set one (and only one) of the following flags:

CRYPT_VERIFYCONTEXT

If this flag is set, then the application will have no access to the key container’s private keys. In fact, if pszContainer is NULL and no default key container is present, the application will have no access to a key container at all.

This option is intended to be used by applications whose only cryptographic need is to verify digital signatures. The only operations normally needed in this case are public key import, hashing, and signature verification.

When CryptAcquireContext is called, many CSPs will require input from the owning user before granting access to the private keys in the key container. For example, the private keys may be encrypted, requiring a password from the user before they can be used. However, if the CRYPT_VERIFYCONTEXT flag is specified, access to the private keys is not required and the user interface can be bypassed.

CRYPT_NEWKEYSET

If this flag is set, then a new key container will be created with the name specified by pszContainer. If pszContainer is NULL, then a key container with the default name will be created.

Note That when key containers are created, most CSPs will not automatically create any public/private key pairs. These keys must be created as a separate step with the CryptGenKey function.

Important This flag should only be set by administrative applications. Normal applications should not create key containers.

CRYPT_DELETEKEYSET

If this flag is set, then the key container specified by pszContainer is deleted. If pszContainer is NULL, then the key container with the default name is deleted. All key pairs in the key container are also destroyed.

When the CRYPT_DELETEKEYSET flag is set, the value returned in phProv is undefined and, thus, the CryptReleaseContext function need not be called afterwards.

Important This flag should only be set by administrative applications. Normal applications should not destroy key containers.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To retrieve extended error information, use the GetLastError function.

The following table lists the error codes most commonly returned by the GetLastError function.

Example

#include <wincrypt.h>



HCRYPTPROV hProv = 0;

BYTE pbData[1000];

DWORD dwDataLen;



// Get handle to the default PROV_RSA_FULL provider.

if(!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, 0)) {

    printf("Error %x during CryptAcquireContext!\n", GetLastError());

    return;

}



// Read the name of the default CSP.

dwDataLen = 1000;

if(!CryptGetProvParam(hProv, PP_NAME, pbData, &dwDataLen, 0)) {

    printf("Error %x reading CSP name!\n", GetLastError());

    return;

}

printf(“Provider name:%s\n”, pbData);



// Read the name of the default key container.

dwDataLen = 1000;

if(!CryptGetProvParam(hProv, PP_CONTAINER, pbData, &dwDataLen, 0)) {

    printf("Error %x reading key container name!\n", GetLastError());

    return;

}

printf(“Key Container name:%s\n”, pbData);



// Perform cryptographic operations.

...



// Release provider handle.

if(!CryptReleaseContext(hProv, 0)) {

    printf("Error %x during CryptReleaseContext!\n", GetLastError());

    return;

}



// ****************************************************************



// Get handle to the Microsoft RSA Base Provider and the 

// "Foo" key container.

if(!CryptAcquireContext(&hProv, TEXT("Foo"), MS_DEF_PROV, 

                        PROV_RSA_FULL, 0)) {

    printf("Error %x during CryptAcquireContext!\n", GetLastError());

    return;

}



// Perform cryptographic operations.

...



// Release provider handle.

if(!CryptReleaseContext(hProv, 0)) {

    printf("Error %x during CryptReleaseContext!\n", GetLastError());

    return;

}



// ****************************************************************



// Get handle to the default provider. Create a new key container 

// named "Bar". Note that this key container will be empty until keys

// are explicitly created with the CryptGenKey function.

lstrcpy(szProv, );

lstrcpy(szContainer, );

if(!CryptAcquireContext(&hProv, TEXT("Bar"), NULL, PROV_RSA_FULL,

                        CRYPT_NEWKEYSET)) {

    printf("Error %x during CryptAcquireContext!\n", GetLastError());

    return;

}



// Perform cryptographic operations.

...



// Release provider handle.

if(!CryptReleaseContext(hProv, 0)) {

    printf("Error %x during CryptReleaseContext!\n", GetLastError());

    return;

}

 

See Also

CryptGenKey, CryptGetProvParam, CryptReleaseContext 

  .