Question

Hello i am searching free api or some easy code to encrypt and decrypt pdf files. Encryption should be done on downloading file from a stream:

            while ((bufferLength = inputStream.read(buffer)) > 0) {

                /*
                 * Writes bufferLength characters starting at 0 in buffer to the target
                 * 
                 * buffer the non-null character array to write. 0 the index
                 * of the first character in buffer to write. bufferLength the maximum
                 * number of characters to write.
                 */
                fileOutput.write(buffer, 0, bufferLength);


            }

And decrypt when need to open with pdf reader. Maybe there are some info, code or free Api for this ?
Someone had done something like this ?

I found myself some code and api. But nothing good for now.

Thanks.

Answer 1

You can try like this using CipherOuputStream and CipherInputStream:

byte[] buf = new byte[1024];

Encryption:

public void encrypt(InputStream in, OutputStream out) {
    try {
        // Bytes written to out will be encrypted
        out = new CipherOutputStream(out, ecipher);

        // Read in the cleartext bytes and write to out to encrypt
        int numRead = 0;
        while ((numRead = in.read(buf)) >= 0) {
            out.write(buf, 0, numRead);
        }
        out.close();
    } catch (java.io.IOException e) {
    }
}

Decryption:

public void decrypt(InputStream in, OutputStream out) {
    try {
        // Bytes read from in will be decrypted
        in = new CipherInputStream(in, dcipher);

        // Read in the decrypted bytes and write the cleartext to out
        int numRead = 0;
        while ((numRead = in.read(buf)) >= 0) {
            out.write(buf, 0, numRead);
        }
        out.close();
    } catch (java.io.IOException e) {
    }
}