Function RSASign

Code (Delphi)

function RSASign(

const AKey: TRSAKey;

const AData: Pointer;

const ADataSize: Cardinal

): TRSASignature; overload;

function RSASign(

const AKey: TRSAKey;

const AData: TEncryptBuffer

): TRSASignature; overload;

function RSASign(

const AKey: TRSAKey;

const AData: RawByteString

): TRSASignature; overload;

Note

Internally RSASign will calculate SHA-1 hash of AData and sign (encrypt) resulting hash with RSA and private key. EMSA-PKCS1-v1_5 scheme is used for padding.

Important!

The resulting signature bytes are in little-endian order. You must reverse bytes order if you want to verify this signature with other tools which requires big-endian order (such as .NET or OpenSSL).

Code (Delphi)

var

// Key to sign data

RSAKey: TRSAKey;

// Data to sign

S: String;

// Digital signature for S

Signature: TRSASignature;

begin

// Load private key

RSAKey := RSALoadPrivateKey('C:\Private.pem', rsText, 'Private key password (if any set)');

try

// Data to sign

S := 'Some data';

// Sign data

Signature := RSASign(RSAKey, Pointer(S), Length(S) * SizeOf(Char));

try

// Clear key as soon as possible

RSADestroyKey(RSAKey);

// Store signature somewhere

edSignature.Text := HexEncodeToString(Signature.pbData, Signature.cbData);

finally

// Free signature once we finished working with it

SecureFree(Signature);

end;

finally

RSADestroyKey(RSAKey);

end;

end;