请教Sha1WithRSA签名的问题，急！

我使用的是D2010，openssl是1.0.0.7（其他版本也试过）,libeay32.pas是从网上下载的0.9.6b
按照百度搜索的文章所说，在libeay32.pas中添加
procedure EVP_MD_CTX_init(ctx: pEVP_MD_CTX); cdecl;
procedure EVP_MD_CTX_cleanup(ctx: pEVP_MD_CTX); cdecl;
function RSA_sign(rsatype: integer; m: PCharacter; m_length: integer;
sigbuf: PCharacter; siglen: Cardinal; rsa: pRSA): integer; cdecl;
procedure EVP_MD_CTX_init; external LIBEAY_DLL_NAME;
procedure EVP_MD_CTX_cleanup; external LIBEAY_DLL_NAME;
function RSA_sign; external LIBEAY_DLL_NAME;

key文件是用openssl工具生成的，可是签名却总是报内存错误
以下是详细代码，请做过的给指点以下，





uses
libeay32, EncdDecd;

function LoadPrivateKey(filename: AnsiString): PEVP_PKEY;
var
bp: PBIO;
A, pkey: PEVP_PKEY;
begin
A := nil;
bp := BIO_new(BIO_s_file());
BIO_read_filename(bp, PAnsiChar(filename));
pkey := PEM_read_bio_PrivateKey(bp, A, nil, NIL);
BIO_free(bp);
Result := pkey;
end;

function Sign(filename, msg: AnsiString): string;
var
ctx: EVP_MD_CTX;
buf_in: PAnsiChar;
m_len, outl: cardinal;
pkey: PEVP_PKEY;
m, buf_out: array [0 .. 1024] of AnsiChar;
p: array [0 .. 255] of AnsiChar;
i: Integer;
begin
buf_out := '';
if filename = '' then
begin
Result := '';
Exit;
end;
ZeroMemory(@m, SizeOf(m));
ZeroMemory(@buf_out, SizeOf(buf_out));
pkey := LoadPrivateKey(filename);
buf_in := PAnsiChar(msg);
EVP_MD_CTX_init(@ctx); // 初始化
EVP_SignInit(@ctx, EVP_sha1());
EVP_SignUpdate(@ctx, buf_in, Length(buf_in));
EVP_DigestFinal(@ctx, m, m_len);
RSA_sign(EVP_sha1()._type, m, m_len, buf_out, outl, pkey.pkey.rsa); //<---------------此处报错
{
---------------------------
Project1
---------------------------
Access violation at address 67A93071 in module 'libeay32.dll'. Read of address EF96BD97.
---------------------------
确定
---------------------------
}
EVP_MD_CTX_cleanup(@ctx);
Result := EncodeString(StrPas(buf_out));
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
OpenSSL_add_all_algorithms;
Sign('d:\rsa_private_key.pem', '123456');
end;