This topic has not yet been rated - Rate this topic

RSACryptoServiceProvider.VerifyHash Method

.NET Framework 4

Updated: August 2010

Verifies that a digital signature is valid by determining the hash value in the signature using the provided public key and comparing it to the provided hash value.

Namespace: System.Security.Cryptography
Assembly: mscorlib (in mscorlib.dll)

Syntax

C++

Copy

public bool VerifyHash(
	byte[] rgbHash,
	string str,
	byte[] rgbSignature
)

Parameters

rgbHash: Type: System.Byte[]
The hash value of the signed data.

str: Type: System.String
The hash algorithm identifier (OID) used to create the hash value of the data.

rgbSignature: Type: System.Byte[]
The signature data to be verified.

Return Value

Type: System.Boolean
true if the signature is valid; otherwise, false.

Exceptions

Exception	Condition
ArgumentNullException	The rgbHash parameter is null. -or- The rgbSignature parameter is null.
CryptographicException	The cryptographic service provider (CSP) cannot be acquired. -or- The signature cannot be verified.

Exception

Condition

ArgumentNullException

The rgbHash parameter is null.

-or-

The rgbSignature parameter is null.

CryptographicException

The cryptographic service provider (CSP) cannot be acquired.

-or-

The signature cannot be verified.

Remarks

This method verifies the RSA digital signature produced by the SignHash method. The signature is verified by obtaining the hash value from the signature using the public key it was signed with, and comparing that value to the hash value of the provided data.

The valid hash algorithms are SHA1 and MD5. The algorithm identifier can be derived from the hash name by using the MapNameToOID method.

Examples

The following example shows how to use the VerifyHash(Byte[], String, Byte[]) method to verify a signature. This code example is part of a larger example provided for the SignHash(Byte[], String) method.

C++

Copy


public bool VerifyHash(RSAParameters rsaParams, byte[] signedData, byte[] signature)
{
    RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();
    SHA1Managed hash = new SHA1Managed();
    byte[] hashedData;

    rsaCSP.ImportParameters(rsaParams);
    bool dataOK = rsaCSP.VerifyData(signedData, CryptoConfig.MapNameToOID("SHA1"), signature);
    hashedData = hash.ComputeHash(signedData);
    return rsaCSP.VerifyHash(hashedData, CryptoConfig.MapNameToOID("SHA1"), signature);
}

Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.