Java

Duplicate openssl req -newkey rsa:2048 -nodes -keyout mydomain.pem -out mydomain.csr

See more OpenSSL Examples

Demonstrates how to duplicate this OpenSSL command:

openssl req -newkey rsa:2048 -nodes -keyout mydomain.pem -out mydomain.csr

This command creates 2 files:

1. mydomain.csr: this is the file to send to DigiCert or Let's Encrypt (or any other CA)
2. mydomain.pem: this is the private key of the domain.

The second file is needed to pair with the certificate that will later be received from the CA.

Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

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

    CkRsa rsa = new CkRsa();

    // Generate a 2048-bit key.  Chilkat RSA supports
    // key sizes ranging from 512 bits to 8192 bits.
    CkPrivateKey privKey = new CkPrivateKey();
    success = rsa.GenKey(2048,privKey);
    if (success == false) {
        System.out.println(rsa.lastErrorText());
        return;
        }

    rsa.UsePrivateKey(privKey);

    // Save the private key to unencrypted PKCS8 PEM
    success = privKey.SavePkcs8PemFile("mydomain.pem");

    // (alternatively) Save the private key to encrypted PKCS8 PEM
    success = privKey.SavePkcs8EncryptedPemFile("myPassword","mydomain_enc.pem");

    // We'll need the private key's modulus for the CSR.
    // The modulus is not something that needs to be protected.  Most people don't realize
    // that a public key is actually just a subset of the private key.  The public parts of
    // an RSA private key are the modulus and exponent.  The exponent is always 65537.
    CkXml privKeyXml = new CkXml();
    success = privKeyXml.LoadXml(privKey.getXml());

    // Get the modulus in base64 format:
    String keyModulus = privKeyXml.getChildContent("Modulus");

    // --------------------------------------------------------------------------------
    // Now build the CSR using Chilkat's ASN.1 API.
    // The keyModulus will be embedded within the ASN.1.

    // A new ASN.1 object is automatically a SEQUENCE.
    // Given that the CSR's root item is a SEQUENCE, we can use
    // this as the root of our CSR.
    CkAsn asnRoot = new CkAsn();

    // Beneath the root, we have a SEQUENCE (the certificate request info), 
    // another SEQUENCE (the algorithm identifier), and a BITSTRING (the signature data)

    success = asnRoot.AppendSequence();
    success = asnRoot.AppendSequence();

    // ----------------------------------
    // Build the Certificate Request Info
    // ----------------------------------
    CkAsn asnCertReqInfo = asnRoot.GetSubItem(0);
    success = asnCertReqInfo.AppendInt(0);

    // Build the Subject part of the Certificate Request Info
    CkAsn asnCertSubject = asnCertReqInfo.AppendSequenceR();

    // Add each subject part..
    CkAsn asnTemp = asnCertSubject.AppendSetR();
    success = asnTemp.AppendSequence2();
    // AppendSequence2 updates the internal reference to the newly appended SEQUENCE.
    // The OID and printable string are added to the SEQUENCE.
    success = asnTemp.AppendOid("2.5.4.6");
    success = asnTemp.AppendString("printable","US");

    asnTemp = asnCertSubject.AppendSetR();
    success = asnTemp.AppendSequence2();
    success = asnTemp.AppendOid("2.5.4.8");
    success = asnTemp.AppendString("utf8","Utah");

    asnTemp = asnCertSubject.AppendSetR();
    success = asnTemp.AppendSequence2();
    success = asnTemp.AppendOid("2.5.4.7");
    success = asnTemp.AppendString("utf8","Lindon");

    asnTemp = asnCertSubject.AppendSetR();
    success = asnTemp.AppendSequence2();
    success = asnTemp.AppendOid("2.5.4.10");
    success = asnTemp.AppendString("utf8","DigiCert Inc.");

    asnTemp = asnCertSubject.AppendSetR();
    success = asnTemp.AppendSequence2();
    success = asnTemp.AppendOid("2.5.4.11");
    success = asnTemp.AppendString("utf8","DigiCert");

    asnTemp = asnCertSubject.AppendSetR();
    success = asnTemp.AppendSequence2();
    success = asnTemp.AppendOid("2.5.4.3");
    success = asnTemp.AppendString("utf8","example.digicert.com");

    // Build the Public Key Info part of the Certificate Request Info
    CkAsn asnPubKeyInfo = asnCertReqInfo.AppendSequenceR();

    CkAsn asnPubKeyAlgId = asnPubKeyInfo.AppendSequenceR();
    success = asnPubKeyAlgId.AppendOid("1.2.840.113549.1.1.1");
    success = asnPubKeyAlgId.AppendNull();

    // The public key itself is a BIT STRING, but the bit string is composed of ASN.1
    // for the RSA public key.  We'll first build the RSA ASN.1 for the public key
    // (containing the 2048 bit modulus and exponent), and encoded it to DER, and then add
    // the DER bytes as a BIT STRING (as a sub-item of asnPubKeyInfo)

    // This is already a SEQUENCE..
    CkAsn asnRsaKey = new CkAsn();

    // The RSA modulus is a big integer.
    success = asnRsaKey.AppendBigInt(keyModulus,"base64");
    success = asnRsaKey.AppendInt(65537);

    String rsaKeyDerBase64 = asnRsaKey.getEncodedDer("base64");

    // Now add the RSA key DER as a BIT STRING.
    success = asnPubKeyInfo.AppendBits(rsaKeyDerBase64,"base64");

    // The last part of the certificate request info is an empty context-specific constructed item
    // with a tag equal to 0.
    success = asnCertReqInfo.AppendContextConstructed(0);

    // Get the DER of the asnCertReqInfo.  
    // This will be signed using the RSA private key.
    CkBinData bdDer = new CkBinData();
    success = asnCertReqInfo.WriteBd(bdDer);

    // Add the signature to the ASN.1
    CkBinData bdSig = new CkBinData();
    success = rsa.SignBd(bdDer,"SHA1",bdSig);
    success = asnRoot.AppendBits(bdSig.getEncoded("base64"),"base64");

    // ----------------------------------
    // Finally, add the algorithm identifier, which is the 2nd sub-item under the root.
    // ----------------------------------
    CkAsn asnAlgId = asnRoot.GetSubItem(1);
    success = asnAlgId.AppendOid("1.2.840.113549.1.1.5");
    success = asnAlgId.AppendNull();

    // Write the CSR to a DER encoded binary file:
    success = asnRoot.WriteBinaryDer("qa_output/mydomain.csr");
    if (success == false) {
        System.out.println(asnRoot.lastErrorText());
        return;
        }

    // It is also possible to get the CSR in base64 format:
    String csrBase64 = asnRoot.getEncodedDer("base64");

    System.out.println("Base64 CSR:");
    System.out.println(csrBase64);
  }
}