CryptVerifySignature function

The CryptVerifySignature function verifies the signature of a hash object.

Before calling this function, CryptCreateHash must be called to create the handle of a hash object. CryptHashData or CryptHashSessionKey is then used to add data or session keys to the hash object.

After CryptVerifySignature completes, only CryptDestroyHash can be called by using the hHash handle.

Syntax

BOOL WINAPI CryptVerifySignature(
  _In_ HCRYPTHASH hHash,
  _In_ BYTE       *pbSignature,
  _In_ DWORD      dwSigLen,
  _In_ HCRYPTKEY  hPubKey,
  _In_ LPCTSTR    sDescription,
  _In_ DWORD      dwFlags
);

Parameters

hHash [in]

A handle to the hash object to verify.

pbSignature [in]

The address of the signature data to be verified.

dwSigLen [in]

The number of bytes in the pbSignature signature data.

hPubKey [in]

A handle to the public key to use to authenticate the signature. This public key must belong to the key pair that was originally used to create the digital signature.

sDescription [in]

This parameter should no longer be used and must be set to NULL to prevent security vulnerabilities. However, it is still supported for backward compatibility in the Microsoft Base Cryptographic Provider.

dwFlags [in]

The following flag values are defined.

Value	Meaning
CRYPT_NOHASHOID 0x00000001	This flag is used with RSA providers. When verifying the signature, the hash object identifier (OID) is not expected to be present or checked. If this flag is not set, the hash OID in the default signature is verified as specified in the definition of DigestInfo in PKCS #7.
CRYPT_TYPE2_FORMAT 0x00000002	This flag is not used.
CRYPT_X931_FORMAT 0x00000004	Use X.931 support for the FIPS 186-2–compliant version of RSA (rDSA).

 

Return value

If the function succeeds, the return value is TRUE.

If the function fails, the return value is FALSE. For extended error information, call GetLastError.

The error codes prefaced by "NTE" are generated by the particular CSP you are using. Some possible error codes follow.

Remarks

The CryptVerifySignature function completes the hash. After this call, no more data can be added to the hash. Additional calls to CryptHashData or CryptHashSessionKey fail. After the application is done with the hash, CryptDestroyHash should be called to destroy the hash object.

If you generate a signature by using the .NET Framework APIs and try to verify it by using the CryptVerifySignature function, the function will fail and GetLastError will return NTE_BAD_SIGNATURE. This is due to the different byte orders between the native Win32 API and the .NET Framework API.

The native cryptography API uses little-endian byte order while the .NET Framework API uses big-endian byte order. If you are verifying a signature generated by using a .NET Framework API, you must swap the order of signature bytes before calling the CryptVerifySignature function to verify the signature.

Examples

For an example that uses the CryptVerifySignature function, see Example C Program: Signing a Hash and Verifying the Hash Signature.

Requirements

See also

Hash and Digital Signature Functions

CryptCreateHash

CryptDestroyHash

CryptHashData

CryptHashSessionKey

CryptSignHash