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<title>The Internet Vagabond :: An Examination of TLS, Part 2</title>
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<a href="/">
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<span class="first">T</span>he
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<span class="first">I</span>nternet
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<span class="first">V</span>agabond
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<article>
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<h1>TLS: An examination into the Security of the Internet, Part 2</h1>
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<p>TLS, more often referred to as SSL, is the means by which a secure
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connection is established over a computer network. Part 1 examines how to
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establish a secure connection using TLS. This article examines further the
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techniques and technology that makes TLS secure. Specifically, a brief
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examination of certificates, cipher suites, and public-key
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authentication.</p>
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<h2>Certificates</h2>
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<p>A certificate is a vessel for a domain to provide authentication
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information. More specifically, and perhaps most importantly, a certificate
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is the package which transfers a key. TLS relies entirely upon Public-Key
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Authentication to setup a secure connection. The challenge with Public-Key
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Authentication is often sharing keys in a verifiable and secure manner.
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This is to say that, despite public keys being public, you still need to
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verify the owner of the key. This is where certificates, and Certificate
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Authorities come in. Each certificate is tailored to a specific domain. It
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includes not only the public key for a user to connect to the server with,
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but also meta-data about the certificate: a UUID, and information about the
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Certificate Authority; a signature authorizing the certificate, as well as
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the encryption used for the signature; a thumbprint of the key, and details
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of the algorithm used to hash the key; and a purpose for the certificate.
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Certificates may contain additional details, but the aforementioned list is
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required.</p>
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<p>A Certificate Authority (CA) is a trusted third-party repository of
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signed keys. The purpose of a CA is very specific: verification. A CA will
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generate and issue a key-pair to a domain. The domain can then share the
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public key using a certificate. How specifically a CA verifies the domains
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and keys is out of scope of this discussion, but Wikipedia provides many
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details on the techniques used.</p>
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<h2>Cipher Suites</h2>
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<p>A cipher is the algorithm used to encrypt information. Ciphers are
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incredibly complex mathematical formulae, and are well beyond my
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understanding. However, it is important to note that the strength of a key
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is only as strong as the cipher suite used to generate it. Likewise, the
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strength of a certificate is only as strong as the cipher used to sign
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it. Keep this in mind when you generate and work with keys.</p>
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<h2>Public-Key Authentication</h2>
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<p>The most important part of TLS is public-key authentication. I would
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argue that public-key authentication is one of the most important facets of
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the technical world. Because of this, I want to recap in more general terms
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how public-key authentication works:</p>
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<ol>
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<li>Two parties want to establish a secure connection.</li>
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<li>Each party generates two keys: one to share publicly, one to keep
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secret.</li>
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<li>Each party then shares their public keys.</li>
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</ol>
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<p>Now, whenever one of the two parties wants to securely communicate with
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the other, they "sign" (encrypt) the communication with their private key.
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The second party can then use the public key of the first party to verify
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the identify of the sender, and decrypt the message.
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<h2>Conclusion</h2>
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<p>Security is a very deep and involved topic, but one I feel every
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Sys-Admin should know a bit about. While these posts are only meant to serve
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as a high-level overview of TLS, there are many more-detailed sources
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available. I would suggest a visit to your local Wikipedia as a good first
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step. Thanks for reading.</p>
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<h1>Sources</h1>
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<ul>
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<li><a href="https://en.wikipedia.org/wiki/Public-key_cryptography">
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Wikipedia: Public-key Cryptography</a></li>
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<li><a
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href="https://security.stackexchange.com/questions/6290/how-is-it-possible-that-people-observing-an-https-connection-being-established-w">Stack
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Exchange: How is it possible that people observing an HTTPS
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connection being established wouldn't know how to decrypt
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it?</a></li>
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<li><a
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href="https://security.stackexchange.com/questions/20803/how-does-ssl-tls-work">
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Stack Exchange: How Does SSL/TLS work?</a></li>
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</ul>
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<!-- ================================= -->
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<!-- ================================= -->
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<!-- Notes (because why remove them?)
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Asymmetric Key Authentication:
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- Relies on two keys: Public key, Private key
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- Both keys are related, but impossible (computationally infeasible) to
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identify the private key based on the public key [1][2]
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- The public key can be distributed publicly
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- Used to encrypt message to the owner of the private paired key
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- Used to verify signatures from the private key
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- The private key is kept secret
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- Used to decrypt message from the public paired key
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- Used to as a digital signature
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Basics of an Asymmetric Key handshake:
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1. Client reaches out to server, requesting a secure connection
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2. Server acknowledges request, sends back it's public key
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- This is commonly known as a certificate. Often signed by a
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third-party to ensure it is what it's supposed to be.
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3. Client uses this public key to encrypt a secret, and sends the package
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back to the server.
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4. The server then uses it's private key to decrypt the public-key
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encrypted secret, and uses that secret hence forth to encrypt all traffic.
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5. A private connection is now established.
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Basics of Certificates
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1. A certificate is a vessel for a server to provide authentication
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information.
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2. Typically a certificate will contain the following information:
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- A UUID of the certificate itself
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- The subject of the certificate
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- The signature, and signature algorithm used
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- The issuer of the certificate, as well as dates when it is valid
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- The purpose of the key
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- The thumbprint, and algorithm, used to hash the key
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- The public key itself
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3. Certificate Authorities act as a third part to verify the integrity of
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public keys.
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-->
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<!-- ================================= -->
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<!-- ================================= -->
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<div class="author_info">
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Bill Niblock
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2015-11-10
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