The usage of cryptography becomes necessary with the requirement for security of communications and data in the modern digital world.
This article will explain the different cryptographic techniques and protocols: digital signatures, message authentication codes (MAC), HMAC, Public key infrastructure-PKI, SSL and TLS, IPsec, PGP, S/MIME, escrowed encryption, and steganography. Each topic will light up their mechanisms, applications, and the reason for their importance.
Implementing Cryptography
1. Digital Signatures
Digital Signatures-are the cryptographic equivalent of handwritten signatures or stamped seals but with far more inherent security. They provide assurance about the authentication and integrity of a message, software, or digital document.
Mechanism
Digital signatures use asymmetric cryptography. The sender creates a hash of a message and encrypts it with their private key. This way, the receiver can decrypt the signature using the sender’s public key to validate the identity of the sender and check the integrity of the message.
Example: Suppose that Alice wants to send a signed document to Bob. She will hash the document and encrypt it with her private key; this is a digital signature. Then Bob receives the document and the signature, computes the hash of the received document, and decrypts the signature using Alice’s public key. As long as the hashes match, Bob would know that the document is authentic and has not been tampered with in any way.
2. MAC: Message Authentication Code
A MAC, or Message Authentication Code, is a small amount of information that is used in the verification process to confirm a message’s authenticity and its integrity. It is generated through a secret key and the message itself.
Mechanism
The sender will append the message with a secret key and process it through a cryptographic hash function or a symmetric encryption algorithm to develop a MAC. A resulting MAC is transmitted with the message.
Example: Consider that Alice sends a message to Bob. After sending the message, she calculates the MAC with the shared secret key and appends the MAC to the message. At the receiving end, Bob will calculate the MAC with the same key and compare it with the received MAC. If they both are the same, then he will be assured that the message is authentic and has not been tampered with.
3. HMAC
HMAC is short for Hash-based Message Authentication Code, a specific type of MAC that utilizes a cryptographic hash function in conjunction with a secret key. As a matter of fact, HMAC provides very strong security and is in use within numerous applications.
Mechanism
HMAC performs the concatenation of a message with a secret key and then hashes it using any hash function to come up with a MAC. In essence, it uses a double hash that provides additional protection against various forms of attack.
Example: Alice wants to send a message with HMAC; she will hash the message concatenated with the secret key, then hash it again with the key. Bob can verify the HMAC by redoing the same calculation with the received message and the shared key.
4. Public Key Infrastructure (PKI)
Public Key Infrastructure-PKI is a framework that enables secure communication based on public and private key pairs. It involves using digital certificates in managing public keys, thereby binding them to identities.
Mechanism
PKI uses Certificate Authorities-CA to issue and manage digital certificates. These certificates, in turn, validate ownership of public keys in various applications, including secure email and SSL/TLS connections.
Example: When any user connects to a HTTPS website, it provides its digital certificate issued by a trusted CA. The client’s browser verifies the validity of the certificate and establishes an encrypted connection using the server’s public key.
5. SSL and TLS
SSL and TLS are cryptographic protocols that ensure secure communication over a computer network. TLS is argued to be the successor of SSL and security enhancements are realized along with it.
Mechanism
The Secure Sockets Layer (SSL)/Transport Layer Security (TLS) protocols make use of both asymmetric and symmetric encryption. The procedures involved in the exchange between the client and the server include authentication and negotiation on the encryption techniques to be used for the session.
For example, when you enter into an HTTPS website, your browser opens a TLS handshake with the server. In response, the server returns its digital certificate; after authentication, the client and the server negotiate a secure session where symmetric encryption is used to transmit data.
6. IPsec
Internet Protocol Security, or IPsec, is a suite of protocols designed to provide authentication and encryption for each IP packet in a communication session for securing the communications of the Internet Protocol.
Mechanism
IPsec works in two modes, namely Transport mode-that encrypts only the payload of the IP packet, and Tunnel mode-which encrypts the entire IP packet. It makes use of protocols such as Authentication Header, which is mainly used for integrity, and Confidentiality Header for encryption.
Example: The most common usage of IPsec is in Virtual Private Networks which can encrypt all the packets of data flowing between the user and the VPN to protect the privacy and security of data while it flows over an insecure network.
7. PGP
Pretty Good Privacy, briefly known as PGP, is a data encryption and decryption software program that provides cryptographic privacy and authentication for data communication. Quite often, it has been used to send secured emails.
Mechanism
PGP uses symmetric and asymmetric encryption in combination. A user sending an encrypted e-mail makes up a symmetric key for the message, encrypts the message with that key, and then encrypts the symmetric key with the recipient’s public key.
Example: If Alice wants to send a secure e-mail to Bob, she encrypts the message with a symmetric key and then encrypts that key with Bob’s public key. With his private key, Bob can decrypt the symmetric key and then use that to decrypt the message.
8. S/MIME
S/MIME or Secure/Multipurpose Internet Mail Extensions – This is actually the standard for the encryption of public key and signing of MIME data. It had been used in securing e-mails by way of authentication, integrity of message, and confidentiality.
Mechanism
S/MIME follows the use of digital certificates in verifying the identity of the sender of the e-mail and maintaining the encryption of its content. Users will be able to send encrypted and digitally signed e-mail messages, where the content of the message is only available to the receiver.
Example: If Alice wants to send an S/MIME email to Bob, she first signs the email using her private key so that Bob will be able to identify her using her public key. Then, she encrypts the content of the email using a symmetric key in such a way that only the recipient is able to decrypt the content.
9. Escrowed Encryption
Escrowed encryption involves the storage of encryption keys by a third party, allowing access by authorized entities under appropriate circumstances. This has been the most common approach in law enforcement and regulatory applications.
Mechanism
In escrowed encryption, the encryption keys are kept safely with the escrow agent, which may give access to the same under certain conditions upon proper request from authorized agencies.
Example: A company could use escrowed encryption to provide protection for sensitive information, but with court order validation, law enforcement has the keys.
10. Steganography
Steganography is the technique of hiding information in other non-secret information. It is difficult to detect because, while cryptography masks the contents of the message, steganography hides the very existence of the message.
Mechanism
Steganography can be performed by embedding secret messages in images, audio, or any other media. This can only be decoded by the person who knows the method of hiding the message.
Example: An image file can carry a hidden message within its pixel information. By slightly changing the least significant bits of the pixel values, a message can be embedded without having any relatively major impact on the appearance of the image.
Conclusion
It has played a major role in securing communications and sensitive data of many applications. Digital signatures, MACs, HMAC, PKI, SSL/TLS, IPsec, PGP, S/MIME, escrowed encryption, and steganography add strong security features against unauthorized access and leakages. Since the cyber threats are continuously developed, knowing how to work effectively with these cryptographic techniques will be a very essential factor in the future integrity and confidentiality of information in our digital world.