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cryptgenkey (advapi32)
 
.
Summary
Generates a random cryptographic key and returns a handle to that key by the reference parameter phKey.

C# Signature:

[DllImport(@"Advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern bool CryptGenKey(
        [In] IntPtr hProv,
        [In] uint Algid,
        [In] uint dwFlags,
        [Out] out IntPtr phKey
    );

VB Signature:

<DLLImport("advapi32.dll", CharSet := CharSet.Auto, SetLastError := True)>
Public Shared Function CryptGenKey(ByVal hProv As IntPtr, ByVal Algid As UInteger, ByVal dwFlags As UInteger, ByRef phKey As IntPtr) As Boolean
End Function

User-Defined Types:

None.

Alternative Managed API:

Do you know one? Please contribute it!

Notes:

be carfeul with the third parameter (dwFlags). It has different meanings depending on the object your are generating. Have a look at the MSDN.

Tips & Tricks:

Those C# enums can be used in conjonction with the function. They are defined in the header WinCrypt.h.

Note that the second parameter of the function (Algid) expects a CryptAlg value.

    /// <summary>
    /// Source: WinCrypt.h
    /// </summary>
    public enum CryptAlgClass : uint
    {
    ALG_CLASS_ANY = (0),
    ALG_CLASS_SIGNATURE = (1 << 13),
    ALG_CLASS_MSG_ENCRYPT = (2 << 13),
    ALG_CLASS_DATA_ENCRYPT = (3 << 13),
    ALG_CLASS_HASH = (4 << 13),
    ALG_CLASS_KEY_EXCHANGE = (5 << 13),
    ALG_CLASS_ALL = (7 << 13)
    }

    /// <summary>
    /// Source: WinCrypt.h
    /// </summary>
    public enum CryptAlgType : uint
    {
    ALG_TYPE_ANY = (0),
    ALG_TYPE_DSS = (1 << 9),
    ALG_TYPE_RSA = (2 << 9),
    ALG_TYPE_BLOCK = (3 << 9),
    ALG_TYPE_STREAM = (4 << 9),
    ALG_TYPE_DH = (5 << 9),
    ALG_TYPE_SECURECHANNEL = (6 << 9)
    }

    /// <summary>
    /// Source: WinCrypt.h
    /// </summary>
    public enum CryptAlgSID : uint
    {
    ALG_SID_ANY = (0),
    ALG_SID_RSA_ANY = 0,
    ALG_SID_RSA_PKCS = 1,
    ALG_SID_RSA_MSATWORK = 2,
    ALG_SID_RSA_ENTRUST = 3,
    ALG_SID_RSA_PGP = 4,
    ALG_SID_DSS_ANY = 0,
    ALG_SID_DSS_PKCS = 1,
    ALG_SID_DSS_DMS = 2,
    ALG_SID_ECDSA = 3,
    ALG_SID_DES = 1,
    ALG_SID_3DES = 3,
    ALG_SID_DESX = 4,
    ALG_SID_IDEA = 5,
    ALG_SID_CAST = 6,
    ALG_SID_SAFERSK64 = 7,
    ALG_SID_SAFERSK128 = 8,
    ALG_SID_3DES_112 = 9,
    ALG_SID_CYLINK_MEK = 12,
    ALG_SID_RC5 = 13,
    ALG_SID_AES_128 = 14,
    ALG_SID_AES_192 = 15,
    ALG_SID_AES_256 = 16,
    ALG_SID_AES = 17,
    ALG_SID_SKIPJACK = 10,
    ALG_SID_TEK = 11,
    ALG_SID_RC2 = 2,
    ALG_SID_RC4 = 1,
    ALG_SID_SEAL = 2,
    ALG_SID_DH_SANDF = 1,
    ALG_SID_DH_EPHEM = 2,
    ALG_SID_AGREED_KEY_ANY = 3,
    ALG_SID_KEA = 4,
    ALG_SID_ECDH = 5,
    ALG_SID_MD2 = 1,
    ALG_SID_MD4 = 2,
    ALG_SID_MD5 = 3,
    ALG_SID_SHA = 4,
    ALG_SID_SHA1 = 4,
    ALG_SID_MAC = 5,
    ALG_SID_RIPEMD = 6,
    ALG_SID_RIPEMD160 = 7,
    ALG_SID_SSL3SHAMD5 = 8,
    ALG_SID_HMAC = 9,
    ALG_SID_TLS1PRF = 10,
    ALG_SID_HASH_REPLACE_OWF = 11,
    ALG_SID_SHA_256 = 12,
    ALG_SID_SHA_384 = 13,
    ALG_SID_SHA_512 = 14,
    ALG_SID_SSL3_MASTER = 1,
    ALG_SID_SCHANNEL_MASTER_HASH = 2,
    ALG_SID_SCHANNEL_MAC_KEY = 3,
    ALG_SID_PCT1_MASTER = 4,
    ALG_SID_SSL2_MASTER = 5,
    ALG_SID_TLS1_MASTER = 6,
    ALG_SID_SCHANNEL_ENC_KEY = 7,
    ALG_SID_ECMQV = 1
    }

    /// <summary>
    /// Source: WinCrypt.h
    /// </summary>
    public enum CryptAlg : uint
    {
    CALG_MD2 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_MD2),
    CALG_MD4 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_MD4),
    CALG_MD5 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_MD5),
    CALG_SHA = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_SHA),
    CALG_SHA1 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_SHA1),
    CALG_MAC = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_MAC),
    CALG_RSA_SIGN = (CryptAlgClass.ALG_CLASS_SIGNATURE | CryptAlgType.ALG_TYPE_RSA | CryptAlgSID.ALG_SID_RSA_ANY),
    CALG_DSS_SIGN = (CryptAlgClass.ALG_CLASS_SIGNATURE | CryptAlgType.ALG_TYPE_DSS | CryptAlgSID.ALG_SID_DSS_ANY),
    CALG_NO_SIGN = (CryptAlgClass.ALG_CLASS_SIGNATURE | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_ANY),
    CALG_RSA_KEYX = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_RSA | CryptAlgSID.ALG_SID_RSA_ANY),
    CALG_DES = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_DES),
    CALG_3DES_112 = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_3DES_112),
    CALG_3DES = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_3DES),
    CALG_DESX = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_DESX),
    CALG_RC2 = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_RC2),
    CALG_RC4 = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_STREAM | CryptAlgSID.ALG_SID_RC4),
    CALG_SEAL = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_STREAM | CryptAlgSID.ALG_SID_SEAL),
    CALG_DH_SF = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_DH | CryptAlgSID.ALG_SID_DH_SANDF),
    CALG_DH_EPHEM = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_DH | CryptAlgSID.ALG_SID_DH_EPHEM),
    CALG_AGREEDKEY_ANY = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_DH | CryptAlgSID.ALG_SID_AGREED_KEY_ANY),
    CALG_KEA_KEYX = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_DH | CryptAlgSID.ALG_SID_KEA),
    CALG_HUGHES_MD5 = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_MD5),
    CALG_SKIPJACK = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_SKIPJACK),
    CALG_TEK = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_TEK),
    CALG_CYLINK_MEK = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_CYLINK_MEK),
    CALG_SSL3_SHAMD5 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_SSL3SHAMD5),
    CALG_SSL3_MASTER = (CryptAlgClass.ALG_CLASS_MSG_ENCRYPT | CryptAlgType.ALG_TYPE_SECURECHANNEL | CryptAlgSID.ALG_SID_SSL3_MASTER),
    CALG_SCHANNEL_MASTER_HASH = (CryptAlgClass.ALG_CLASS_MSG_ENCRYPT | CryptAlgType.ALG_TYPE_SECURECHANNEL | CryptAlgSID.ALG_SID_SCHANNEL_MASTER_HASH),
    CALG_SCHANNEL_MAC_KEY = (CryptAlgClass.ALG_CLASS_MSG_ENCRYPT | CryptAlgType.ALG_TYPE_SECURECHANNEL | CryptAlgSID.ALG_SID_SCHANNEL_MAC_KEY),
    CALG_SCHANNEL_ENC_KEY = (CryptAlgClass.ALG_CLASS_MSG_ENCRYPT | CryptAlgType.ALG_TYPE_SECURECHANNEL | CryptAlgSID.ALG_SID_SCHANNEL_ENC_KEY),
    CALG_PCT1_MASTER = (CryptAlgClass.ALG_CLASS_MSG_ENCRYPT | CryptAlgType.ALG_TYPE_SECURECHANNEL | CryptAlgSID.ALG_SID_PCT1_MASTER),
    CALG_SSL2_MASTER = (CryptAlgClass.ALG_CLASS_MSG_ENCRYPT | CryptAlgType.ALG_TYPE_SECURECHANNEL | CryptAlgSID.ALG_SID_SSL2_MASTER),
    CALG_TLS1_MASTER = (CryptAlgClass.ALG_CLASS_MSG_ENCRYPT | CryptAlgType.ALG_TYPE_SECURECHANNEL | CryptAlgSID.ALG_SID_TLS1_MASTER),
    CALG_RC5 = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_RC5),
    CALG_HMAC = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_HMAC),
    CALG_TLS1PRF = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_TLS1PRF),
    CALG_HASH_REPLACE_OWF = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_HASH_REPLACE_OWF),
    CALG_AES_128 = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_AES_128),
    CALG_AES_192 = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_AES_192),
    CALG_AES_256 = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_AES_256),
    CALG_AES = (CryptAlgClass.ALG_CLASS_DATA_ENCRYPT | CryptAlgType.ALG_TYPE_BLOCK | CryptAlgSID.ALG_SID_AES),
    CALG_SHA_256 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_SHA_256),
    CALG_SHA_384 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_SHA_384),
    CALG_SHA_512 = (CryptAlgClass.ALG_CLASS_HASH | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_SHA_512),
    CALG_ECDH = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_DH | CryptAlgSID.ALG_SID_ECDH),
    CALG_ECMQV = (CryptAlgClass.ALG_CLASS_KEY_EXCHANGE | CryptAlgType.ALG_TYPE_ANY | CryptAlgSID.ALG_SID_ECMQV),
    CALG_ECDSA = (CryptAlgClass.ALG_CLASS_SIGNATURE | CryptAlgType.ALG_TYPE_DSS | CryptAlgSID.ALG_SID_ECDSA)
    }

Sample Code:

Create a 2048 bits RSA Signing key pair:

/// NOTE: hProv is a valid context handle see: CryptAquireContext
uint keySize = 2048;
IntPtr hKey = IntPtr.Zero;
/// Put the key size in the upper 16 bits
uint dwFlags = keySize << 16;
/// NOTE: Some additional flags can be set in dwFlags. Just OR them :
///       dwFlags |= someFlag;
CryptGenKey(hProv, (uint)CryptAlg.CALG_RSA_SIGN, dwFlags, out hKey);

Documentation
CryptGenKey on MSDN

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