I found that when i opened https://huynhsamha.github.io/crypto/algorithm/sha256, I actually received a 404 as a response. I think your workaround for hosting SPA on GitHub using the 404.html is the issue here. While us humans see your app being served on our browser correctly, googlebot doesn't care and just look at the response code and see that it has received a 404. You'll need a different workaround that doesn't involves using the 404.html as the entry point to your app directly.
Try following this workaround by rafrex instead, it redirects the browser to index.html using the 404.html while keeping the original route, it claims that googlebot register that as a 301 instead of a 404, for your case that means adding these changes below to your site, pay attention to the script below the <!-- ------Single Page Apps GitHub Pages Workaround------ -->:
<!-- 404.html -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Cryptography</title>
<!-- ------Single Page Apps GitHub Pages Workaround------ -->
<script type="text/javascript">
// Single Page Apps for GitHub Pages
// https://github.com/rafrex/spa-github-pages
// Copyright (c) 2016 Rafael Pedicini, licensed under the MIT License
// ----------------------------------------------------------------------
// This script takes the current url and converts the path and query
// string into just a query string, and then redirects the browser
// to the new url with only a query string and hash fragment,
// e.g. http://www.foo.tld/one/two?a=b&c=d#qwe, becomes
// http://www.foo.tld/?p=/one/two&q=a=b~and~c=d#qwe
// Note: this 404.html file must be at least 512 bytes for it to work
// with Internet Explorer (it is currently > 512 bytes)
// If you're creating a Project Pages site and NOT using a custom domain,
// then set segmentCount to 1 (enterprise users may need to set it to > 1).
// This way the code will only replace the route part of the path, and not
// the real directory in which the app resides, for example:
// https://username.github.io/repo-name/one/two?a=b&c=d#qwe becomes
// https://username.github.io/repo-name/?p=/one/two&q=a=b~and~c=d#qwe
// Otherwise, leave segmentCount as 0.
var segmentCount = 1;
var l = window.location;
l.replace(
l.protocol + '//' + l.hostname + (l.port ? ':' + l.port : '') +
l.pathname.split('/').slice(0, 1 + segmentCount).join('/') + '/?p=/' +
l.pathname.slice(1).split('/').slice(segmentCount).join('/').replace(/&/g, '~and~') +
(l.search ? '&q=' + l.search.slice(1).replace(/&/g, '~and~') : '') +
l.hash
);
</script>
</head>
<body>
</body>
</html>
<!-- index.html -->
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<meta name="theme-color" content="#000000">
<meta name="description" content="Cryptography Algorithms: Secure Hash Algorithm (sha256, sha512, ...), Message Digest Algorithm (md5, ripemd160), HMAC-SHA, HMAC-MD, pbkdf2, Advanced Encryption Standard (AES), Triple Data Encryption Standard, (TripleDES, DES), RC4, Rabbit, ...">
<meta name="keywords" content="crypto, algorithms, secure hash, sha, sha512, sha256, message digest, md5, hmac-sha, aes, des, tripledes, pbkdf2, rc4, rabbit, encryption, descryption">
<meta name="author" content="huynhsamha">
<!-- Open Graph -->
<meta property="fb:app_id" content="440168923127908">
<meta property="og:url" content="https://huynhsamha.github.io/crypto">
<meta property="og:title" content="Cryptography Algorithms">
<meta property="og:description" content="Cryptography Algorithms: Secure Hash Algorithm (sha256, sha512, ...), Message Digest Algorithm (md5, ripemd160), HMAC-SHA, HMAC-MD, pbkdf2, Advanced Encryption Standard (AES), Triple Data Encryption Standard, (TripleDES, DES), RC4, Rabbit, ...">
<meta property="og:type" content="website">
<meta property="og:image" content="%PUBLIC_URL%/img/main.jpeg">
<meta property="og:site_name" content="Cryptography">
<meta property="og:locale" content="vi_VN">
<!-- Twitter Card -->
<meta name="twitter:card" content="summary">
<meta name="twitter:site" content="@huynhsamha">
<meta name="twitter:creator" content="@huynhsamha">
<meta name="twitter:url" content="https://huynhsamha.github.io/crypto">
<meta name="twitter:title" content="Cryptography Algorithms">
<meta name="twitter:description" content="Cryptography Algorithms: Secure Hash Algorithm (sha256, sha512, ...), Message Digest Algorithm (md5, ripemd160), HMAC-SHA, HMAC-MD, pbkdf2, Advanced Encryption Standard (AES), Triple Data Encryption Standard, (TripleDES, DES), RC4, Rabbit, ...">
<meta name="twitter:image:src" content="%PUBLIC_URL%/img/main.jpeg">
<!--
manifest.json provides metadata used when your web app is added to the
homescreen on Android. See https://developers.google.com/web/fundamentals/engage-and-retain/web-app-manifest/
-->
<link rel="manifest" href="%PUBLIC_URL%/manifest.json">
<link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
<link rel="author" href="//github.com/huynhsamha">
<link rel="canonical" href="//huynhsamha.github.io/crypto">
<!--
Notice the use of %PUBLIC_URL% in the tags above.
It will be replaced with the URL of the `public` folder during the build.
Only files inside the `public` folder can be referenced from the HTML.
Unlike "/favicon.ico" or "favicon.ico", "%PUBLIC_URL%/favicon.ico" will
work correctly both with client-side routing and a non-root public URL.
Learn how to configure a non-root public URL by running `npm run build`.
-->
<link href="//fonts.googleapis.com/css?family=Open+Sans:400,600,700&subset=vietnamese" rel="stylesheet">
<link rel="stylesheet" href="%PUBLIC_URL%/css/bootstrap.min.css">
<link rel="stylesheet" href="%PUBLIC_URL%/lib/font-awesome/css/font-awesome.min.css">
<!-- ------Single Page Apps GitHub Pages Workaround------ -->
<script type="text/javascript">
// Single Page Apps for GitHub Pages
// https://github.com/rafrex/spa-github-pages
// Copyright (c) 2016 Rafael Pedicini, licensed under the MIT License
// ----------------------------------------------------------------------
// This script checks to see if a redirect is present in the query string
// and converts it back into the correct url and adds it to the
// browser's history using window.history.replaceState(...),
// which won't cause the browser to attempt to load the new url.
// When the single page app is loaded further down in this file,
// the correct url will be waiting in the browser's history for
// the single page app to route accordingly.
(function(l) {
if (l.search) {
var q = {};
l.search.slice(1).split('&').forEach(function(v) {
var a = v.split('=');
q[a[0]] = a.slice(1).join('=').replace(/~and~/g, '&');
});
if (q.p !== undefined) {
window.history.replaceState(null, null,
l.pathname.slice(0, -1) + (q.p || '') +
(q.q ? ('?' + q.q) : '') +
l.hash
);
}
}
}(window.location))
</script>
<title>Cryptography</title>
</head>
<body>
<noscript>
You need to enable JavaScript to run this app.
</noscript>
<div id="root"></div>
<!--
This HTML file is a template.
If you open it directly in the browser, you will see an empty page.
You can add webfonts, meta tags, or analytics to this file.
The build step will place the bundled scripts into the <body> tag.
To begin the development, run `npm start` or `yarn start`.
To create a production bundle, use `npm run build` or `yarn build`.
-->
<script src="%PUBLIC_URL%/js/jquery-3.3.1.slim.min.js" type="text/javascript"></script>
<script src="%PUBLIC_URL%/js/popper.min.js" type="text/javascript"></script>
<script src="%PUBLIC_URL%/js/bootstrap.min.js" type="text/javascript"></script>
<!-- Google Adsense -->
<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
</body>
</html>
More info and discussions on GitHub's support for single page app here.
