captcha.md

Captcha Security

Captcha is used to prevent automated requests and bots.

How it works

• The CaptchaUtil class generates image-based captchas.
• Captchas are encoded in Base64 and sent to the client.
• The client must solve the captcha to proceed with certain requests.

Main Class

• CaptchaUtil: Generates and encodes captchas.

Example

Captcha captcha = CaptchaUtil.createCaptcha(200, 50);
String base64Image = CaptchaUtil.encodeCaptcha(captcha);

Creates a captcha image and encodes it to Base64 for sending to the client.

Captcha Generation

// CaptchaUtil.java
public static Captcha createCaptcha(int width, int height){
    return new Captcha.Builder(width, height)
            .addText()
            .addBackground()
            .addNoise()
            .build();
}

Generates a captcha image with text, background, and noise.

Captcha Encoding

// CaptchaUtil.java
public static String encodeCaptcha(Captcha c){
    try(ByteArrayOutputStream o = new ByteArrayOutputStream()){
        ImageIO.write(c.getImage(), "png", o);
        return Base64.getEncoder().encodeToString(o.toByteArray());
    } catch (IOException e){
        throw new RuntimeException("error encoding Captcha", e);
    }
}

Encodes the captcha image to a Base64 string for easy transmission.