Unicode C

RSA SHA256 Signature using Private Key from Java Keystore

See more RSA Examples

Signs plaintext using RSA SHA256 using a key from a Java keystore.

Duplicatest this code:

KeyStore keystore; // key repository for keys containing signature certificate
String alias; // alias for the certificate in the key repository
String password; // password for the certificate's private key
String plaintext; // text being signed


Signature signature = Signature.getInstance("SHA256withRSA");
signature.initSign((PrivateKey) keystore.getKey(alias, password.toCharArray()));
signature.update(plaintext.getBytes("UTF-8"));
byte[] rsa_text= signature.sign();

Unicode C

#include <C_CkJavaKeyStoreW.h>
#include <C_CkPrivateKeyW.h>
#include <C_CkRsaW.h>
#include <C_CkByteData.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkJavaKeyStoreW jks;
    const wchar_t *jksPassword;
    const wchar_t *privKeyPassword;
    BOOL caseSensitive;
    HCkPrivateKeyW privKey;
    HCkRsaW rsa;
    HCkByteData binarySignature;
    const wchar_t *plaintext;
    const wchar_t *signatureStr;

    success = FALSE;

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

    jks = CkJavaKeyStoreW_Create();

    jksPassword = L"secret";

    //  Load the Java keystore from a file.  The JKS file password is used
    //  to verify the keyed digest that is found at the very end of the keystore.
    //  It verifies that the keystore has not been modified.
    success = CkJavaKeyStoreW_LoadFile(jks,jksPassword,L"qa_data/jks/sample_secret.jks");
    if (success == FALSE) {
        wprintf(L"%s\n",CkJavaKeyStoreW_lastErrorText(jks));
        CkJavaKeyStoreW_Dispose(jks);
        return;
    }

    //  Get the private key from the JKS.
    //  The private key password may be different than the file password.
    privKeyPassword = L"secret";
    caseSensitive = FALSE;
    privKey = CkPrivateKeyW_Create();
    success = CkJavaKeyStoreW_PrivateKeyOf(jks,privKeyPassword,L"some.alias",caseSensitive,privKey);
    if (success == FALSE) {
        wprintf(L"%s\n",CkJavaKeyStoreW_lastErrorText(jks));
        CkJavaKeyStoreW_Dispose(jks);
        CkPrivateKeyW_Dispose(privKey);
        return;
    }

    //  Establish the RSA object and tell it to use the private key..
    rsa = CkRsaW_Create();

    success = CkRsaW_UsePrivateKey(rsa,privKey);
    if (success == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        CkJavaKeyStoreW_Dispose(jks);
        CkPrivateKeyW_Dispose(privKey);
        CkRsaW_Dispose(rsa);
        return;
    }

    //  Indicate we'll be signing the utf-8 byte representation of the string..
    CkRsaW_putCharset(rsa,L"utf-8");

    //  Sign some plaintext using RSA-SHA256
    binarySignature = CkByteData_Create();
    plaintext = L"this is the text to be signed";
    success = CkRsaW_SignString(rsa,plaintext,L"SHA256",binarySignature);
    if (CkRsaW_getLastMethodSuccess(rsa) == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        CkJavaKeyStoreW_Dispose(jks);
        CkPrivateKeyW_Dispose(privKey);
        CkRsaW_Dispose(rsa);
        CkByteData_Dispose(binarySignature);
        return;
    }

    //  Alternatively, if the signature is desired in some encoded string form,
    //  such as base64, base64-url, hex, etc.
    CkRsaW_putEncodingMode(rsa,L"base64-url");
    signatureStr = CkRsaW_signStringENC(rsa,plaintext,L"SHA256");
    wprintf(L"base64-url RSA signature: %s\n",signatureStr);


    CkJavaKeyStoreW_Dispose(jks);
    CkPrivateKeyW_Dispose(privKey);
    CkRsaW_Dispose(rsa);
    CkByteData_Dispose(binarySignature);

    }