Delphi DLL Requires Chilkat v11.0.0+

RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature. Delphi DLL

var
success: Boolean;
privKey: HCkPrivateKey;
rsa: HCkRsa;
strData: PWideChar;
hexSig: PWideChar;
cert: HCkCert;
pubKey: HCkPublicKey;
rsa2: HCkRsa;

begin
success := False;

//  This example assumes the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

privKey := CkPrivateKey_Create();

//  Load the private key from an RSA .key file:
success := CkPrivateKey_LoadPemFile(privKey,'privateKey.key');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

rsa := CkRsa_Create();

//  Import the private key into the RSA component:
success := CkRsa_UsePrivateKey(rsa,privKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

//  Create the signature as a hex string:
CkRsa_putEncodingMode(rsa,'hex');

strData := 'This is the string to be signed.';

//  Sign the string using the sha256 hash algorithm.
//  Other valid choices are "md2", "sha1", "sha384",
//  "sha512", and "md5".
hexSig := CkRsa__signStringENC(rsa,strData,'sha256');

Memo1.Lines.Add(hexSig);

//  Load a digital certificate from a .cer file:
cert := CkCert_Create();

success := CkCert_LoadFromFile(cert,'myCert.cer');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

pubKey := CkPublicKey_Create();
CkCert_GetPublicKey(cert,pubKey);

//  Now verify using a new instance of the RSA object:
rsa2 := CkRsa_Create();

//  Import the public key into the RSA object:
success := CkRsa_UsePublicKey(rsa2,pubKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

//  The signature is a hex string, so make sure the EncodingMode is correct:
CkRsa_putEncodingMode(rsa2,'hex');

//  Verify the signature:
success := CkRsa_VerifyStringENC(rsa2,strData,'sha256',hexSig);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

Memo1.Lines.Add('Success.');

CkPrivateKey_Dispose(privKey);
CkRsa_Dispose(rsa);
CkCert_Dispose(cert);
CkPublicKey_Dispose(pubKey);
CkRsa_Dispose(rsa2);