CEH-Module20 - Cryptography
Website Visitors:Cryptography
Cryptography is the process of encoding data to protect it from unauthorized access, maintain its privacy, and guarantee its secrecy. It involves the use of mathematical principles and algorithms to transform data into a form that appears meaningless to anyone who does not possess the appropriate key or decryption method.
The main purposes of cryptography are to:
- Ensure the confidentiality of digital data by encoding it so that only authorized parties can access it.
- Maintain the integrity of data, preventing it from being modified by unauthorized parties.
- Authenticate the identity of the sender of information.
Cryptography is an essential tool for cybersecurity, used to protect sensitive information such as passwords, emails, financial transactions, and communications. It employs various techniques like symmetric key cryptography, asymmetric cryptography, and hashing to achieve these security goals.
Cryptography has evolved significantly over time, from early ciphers to modern, highly sophisticated algorithms that are virtually unbreakable. The field continues to advance as the need to protect digital information becomes increasingly critical in our interconnected world.
Types of Cryptography
The different types of cryptography include:
-
Symmetric Key Cryptography:
- In this encryption system, both the sender and receiver use a single common key to encrypt and decrypt messages. It is faster and simpler but requires a secure exchange of keys. Popular systems include Data Encryption Standard (DES) and Advanced Encryption Standard (AES).
-
Hash Functions:
- This algorithm calculates a fixed-length hash value based on the plaintext, making it impossible to recover the original content. Hash functions are commonly used in encrypting passwords and ensuring data integrity.
-
Asymmetric Key Cryptography:
- This type uses a pair of keys for encryption and decryption. The receiver’s public key encrypts the information, while the receiver’s private key decrypts it. Even if the public key is known, only the intended receiver can decode the message with their private key. The RSA algorithm is a popular asymmetric key cryptography method.
Cipher
In cryptography, a cipher is a method used to encrypt and decrypt messages to secure communication. Ciphers involve the use of algorithms and keys to transform plaintext (original message) into ciphertext (encrypted message) and vice versa.
Ciphers play a crucial role in ensuring data confidentiality, integrity, and authenticity in various applications such as secure messaging, online transactions, and data storage. It is essential to use strong and well-implemented ciphers to protect sensitive information from unauthorized access and cyber threats.
Ciphers can be broadly categorized into classical and modern ciphers based on their historical development and complexity:
-
Classical Ciphers:
- Substitution Ciphers: These ciphers involve substituting one letter or symbol for another. Examples include the Caesar cipher, Atbash cipher, and the Vigenère cipher.
- Transposition Ciphers: Transposition ciphers involve rearranging the order of letters in the plaintext to create the ciphertext. Examples include the Rail Fence cipher and the Columnar Transposition cipher.
-
Modern Ciphers:
- Block Ciphers: Block ciphers encrypt fixed-size blocks of data at a time. They use symmetric key encryption and are widely used in modern cryptography. Examples include the Data Encryption Standard (DES) and the Advanced Encryption Standard (AES).
- Stream Ciphers: Stream ciphers encrypt data bit by bit or byte by byte. They are often faster than block ciphers and are commonly used in applications like wireless communication and real-time encryption. Examples include the RC4 cipher and the ChaCha20 stream cipher.
- Public-Key Cryptography: Public-key cryptography, also known as asymmetric cryptography, uses a pair of keys (public and private) for encryption and decryption. It enables secure communication over insecure channels without the need to share a secret key. Examples include the RSA algorithm and Elliptic Curve Cryptography (ECC).
Both classical and modern ciphers have their strengths and weaknesses. While classical ciphers are often simpler and easier to understand, they are more vulnerable to modern cryptanalysis techniques. Modern ciphers, on the other hand, provide stronger security guarantees and are designed to withstand sophisticated attacks in today’s digital age.
DES (Data Encryption Standard) & AES (Advanced Encryption Standard)
DES (Data Encryption Standard) and AES (Advanced Encryption Standard) are two widely used symmetric block ciphers in modern cryptography:
-
Data Encryption Standard (DES):
- DES is a symmetric key algorithm that uses a 56-bit key to encrypt and decrypt data in 64-bit blocks.
- Developed in the 1970s, DES was the standard encryption algorithm for many years until it was replaced by AES due to its vulnerability to brute-force attacks.
- DES operates through a series of 16 rounds of substitution and permutation (S-boxes and P-boxes) to transform plaintext into ciphertext.
- Despite its strength at the time of its creation, DES is now considered insecure due to its short key length, making it susceptible to exhaustive key search attacks.
-
Advanced Encryption Standard (AES):
- AES is a symmetric block cipher that uses keys of 128, 192, or 256 bits to encrypt and decrypt data in blocks of 128 bits.
- Selected through a public competition by the National Institute of Standards and Technology (NIST) in 2001, AES is now the standard encryption algorithm used worldwide.
- AES operates through multiple rounds of substitution, permutation, and mixing operations (SubBytes, ShiftRows, MixColumns, AddRoundKey) to provide strong security against various cryptographic attacks.
- AES is known for its efficiency, security, and resistance to attacks, making it suitable for securing sensitive data in various applications such as banking, e-commerce, and communication.
In summary, while DES was a groundbreaking encryption algorithm in its time, AES has replaced it as the industry standard due to its superior security features and resistance to attacks. AES offers a higher level of security with longer key lengths and more robust encryption processes, making it the preferred choice for secure communication and data protection in modern cryptographic applications.
RC4, RC5 & RC6
RC4, RC5, and RC6 are symmetric key algorithms developed by Ron Rivest at RSA Security. Here is an overview of each algorithm:
-
RC4 (Rivest Cipher 4):
- RC4 is a stream cipher known for its simplicity and speed in encrypting data.
- It operates by generating a pseudorandom stream of bits based on a secret key, which is then XORed with the plaintext to produce the ciphertext.
- RC4 was widely used in various applications, including wireless networks, SSL/TLS protocols, and secure communication.
- However, RC4 has been found to have vulnerabilities over the years, leading to its deprecation in many security protocols due to weaknesses in its key scheduling algorithm.
-
RC5 (Rivest Cipher 5):
- RC5 is a block cipher designed to be more secure than RC4 by using a variable block size, key size, and number of rounds.
- It operates through a series of modular arithmetic operations, including modular addition and rotation, to encrypt and decrypt data.
- RC5 allows for flexibility in key size (up to 2040 bits) and block size (32, 64, or 128 bits), making it adaptable to different security requirements.
- While RC5 has not gained as much popularity as AES, it is still considered a secure encryption algorithm when implemented correctly.
-
RC6 (Rivest Cipher 6):
- RC6 is an extension of the RC5 algorithm, designed to provide improved security and performance.
- It uses a 128-bit block size and supports key lengths of 128, 192, or 256 bits.
- RC6 operates through a combination of modular arithmetic, bitwise XOR, and multiplication operations to encrypt and decrypt data.
- RC6 was a candidate in the AES selection process but was not chosen as the standard algorithm. Nonetheless, it remains a strong encryption algorithm for various applications.
Overall, RC4, RC5, and RC6 are encryption algorithms developed by Ron Rivest, each offering different features and levels of security. While RC4 has known vulnerabilities and is no longer recommended for secure communication, RC5 and RC6 provide stronger encryption capabilities and can be used in applications where their specific features are advantageous.
Rivest Shamir Adleman (RSA)
RSA (Rivest-Shamir-Adleman) is a widely used asymmetric cryptographic algorithm named after its inventors Ron Rivest, Adi Shamir, and Leonard Adleman. Here are key points about RSA:
-
Key Generation:
- RSA uses a pair of keys: a public key for encryption and a private key for decryption.
- The keys are generated using large prime numbers, and the security of RSA relies on the difficulty of factoring the product of two large prime numbers.
-
Encryption and Decryption:
- To encrypt a message using RSA, the sender uses the recipient’s public key to transform the plaintext into ciphertext.
- To decrypt the ciphertext, the recipient uses their private key to recover the original plaintext.
-
Digital Signatures:
- RSA can also be used for digital signatures to provide data integrity and authentication.
- A sender signs a message with their private key, and the recipient verifies the signature using the sender’s public key.
-
Security:
- RSA is considered secure when using sufficiently large key sizes. Common key lengths are 2048 bits or 4096 bits.
- The security of RSA relies on the difficulty of factoring large composite numbers, which forms the basis of its security.
-
Applications:
- RSA is widely used in secure communication protocols like SSL/TLS, SSH, and PGP for securing data transmission over networks.
- It is also used in digital signatures, secure email, secure web browsing, and other applications requiring secure encryption and authentication.
-
Performance:
- RSA encryption and decryption operations can be computationally intensive, especially with larger key sizes.
- Asymmetric algorithms like RSA are often used in combination with symmetric algorithms for a more efficient hybrid encryption approach.
Overall, RSA is a fundamental asymmetric encryption algorithm that plays a crucial role in securing communication, data integrity, and authentication in various applications. Its security and versatility have made it a cornerstone of modern cryptography.
Diffie-Hellman
Diffie-Hellman is a key exchange algorithm that allows two parties to securely establish a shared secret key over an insecure communication channel. Here are key points about the Diffie-Hellman algorithm:
-
Key Exchange:
- Diffie-Hellman enables two parties to agree on a shared secret key without explicitly exchanging the key over the communication channel.
- The shared secret key can then be used for symmetric encryption to secure further communication between the parties.
-
Public-Key Cryptography:
- Diffie-Hellman is based on public-key cryptography, where each party has a public-private key pair.
- The public keys are exchanged openly, while the private keys are kept secret.
-
Algorithm Steps:
- Both parties agree on public parameters: a large prime number (p) and a base (g) that is a primitive root modulo p.
- Each party generates their private key (a and b) and calculates their public key (A and B) using the shared parameters.
- The parties exchange their public keys (A and B) over the insecure channel.
- Using their private key and the received public key, each party independently computes the shared secret key.
-
Security:
- The security of Diffie-Hellman relies on the discrete logarithm problem, which is computationally difficult to solve.
- Even if an eavesdropper intercepts the public keys exchanged during the key exchange, it is computationally infeasible to derive the shared secret key without knowledge of the private keys.
-
Perfect Forward Secrecy:
- Diffie-Hellman provides perfect forward secrecy, meaning that even if the long-term private keys are compromised in the future, past communications remain secure because the shared secret key is ephemeral.
-
Applications:
- Diffie-Hellman is widely used in secure communication protocols like SSL/TLS, SSH, and IPsec for establishing secure connections.
- It is also used in VPNs, secure messaging applications, and any scenario where secure key exchange is required.
Overall, Diffie-Hellman key exchange is a fundamental algorithm in modern cryptography that enables secure communication by establishing shared secret keys between parties without the need to transmit the keys over the insecure channel.
Message Digest (one-way hash) Functions
Message digest functions, also known as one-way hash functions, are cryptographic algorithms that take an input (message) of any size and produce a fixed-size output called a hash value or digest. Here are key points about message digest one-way hash functions:
-
One-Way Property:
- One of the essential properties of message digest functions is that they are one-way functions, meaning it is computationally infeasible to reverse the process and obtain the original input from the hash value.
- Given a hash value, it should be difficult to find a different input that produces the same hash value (collision resistance).
-
Fixed Output Size:
- Message digest functions produce a fixed-size output, regardless of the size of the input message.
- Common hash functions like SHA-256 (producing a 256-bit hash) and MD5 (producing a 128-bit hash) are widely used in practice.
-
Data Integrity:
- Message digest functions are commonly used to ensure data integrity by generating a hash value for a message and comparing it at the receiving end to verify that the message has not been altered during transmission.
-
Digital Signatures:
- Hash functions are an integral part of digital signatures. A sender can hash a message and then encrypt the hash value with their private key to create a digital signature.
- The recipient can verify the digital signature by decrypting it with the sender’s public key and comparing the decrypted hash value with the hash of the received message.
-
Applications:
- Message digest functions are used in various cryptographic applications, including password hashing, digital signatures, data integrity verification, and secure communication protocols.
- Commonly used hash functions include SHA (Secure Hash Algorithm) family (e.g., SHA-1, SHA-256, SHA-3) and MD5 (Message Digest Algorithm 5).
-
Security Considerations:
- It is important to use secure and collision-resistant hash functions to prevent attacks like birthday attacks and collision attacks.
- As computing power increases, older hash functions like MD5 and SHA-1 are being deprecated in favor of more secure alternatives like SHA-256 and SHA-3.
Overall, message digest one-way hash functions play a crucial role in ensuring data integrity, authentication, and security in various cryptographic applications by providing a fixed-size representation of data that uniquely identifies its content.
Other Encryption Techniques
-
TPM (Trusted Platform Module): TPM is a hardware-based security feature that is used to securely store sensitive information, such as encryption keys, digital certificates, and passwords. It provides a secure way to protect and manage cryptographic keys used for encryption.
-
HSM (Hardware Security Module): HSM is a physical computing device that safeguards and manages digital keys for strong authentication and provides encryption and decryption services. It is often used to secure sensitive data and transactions in various applications, such as banking, e-commerce, and cloud services.
-
USB encryption: USB encryption refers to the process of encrypting data stored on a USB flash drive or external hard drive to protect it from unauthorized access. This encryption ensures that the data is secure even if the device is lost or stolen.
-
Hard drive encryption: Hard drive encryption is the process of encrypting the entire contents of a computer’s hard drive to protect the data stored on it. This encryption helps prevent unauthorized access to the data, especially in case the device is lost or stolen.
PKI
PKI stands for Public Key Infrastructure. It is a system of hardware, software, policies, and procedures used to create, manage, distribute, use, store, and revoke digital certificates and public-private key pairs. PKI enables secure communication and transactions over the internet by providing a framework for verifying the authenticity of participants, ensuring the confidentiality and integrity of data, and enabling secure electronic signatures. PKI is commonly used in applications such as secure email, online banking, e-commerce, and secure access to networks and systems.
The components of a Public Key Infrastructure (PKI) typically include the following:
-
Certificate Authority (CA): A trusted entity that issues digital certificates to users, devices, and services. The CA verifies the identity of the certificate holder and signs the digital certificate to attest to its authenticity.
-
Registration Authority (RA): An entity that verifies the identity of individuals or organizations requesting digital certificates from the CA. The RA acts as an intermediary between the certificate requester and the CA.
-
Certificate Revocation List (CRL): A list of digital certificates that have been revoked before their expiration date. The CRL is maintained by the CA and is used to inform users and systems not to trust the revoked certificates.
-
Public Key: A cryptographic key that is made public and used for encryption, digital signatures, and verifying the authenticity of digital certificates.
-
Private Key: A cryptographic key that is kept secret and used for decryption, creating digital signatures, and proving the identity of the key holder.
-
Digital Certificate: A digitally signed document that binds a public key to an individual, device, or service. The digital certificate contains information about the certificate holder, the public key, the CA that issued the certificate, and the digital signature of the CA.
-
Certificate Policy (CP) and Certificate Practice Statement (CPS): Documents that define the rules, procedures, and practices followed by the CA in issuing and managing digital certificates. The CP specifies the requirements for certificate issuance, while the CPS describes the operational practices of the CA.
Signed VS Self-Signed Certificate
A signed certificate is issued by a trusted third party known as a Certificate Authority (CA). The CA verifies the identity of the entity requesting the certificate and signs it, indicating that the information in the certificate is valid. Websites and applications commonly use signed certificates to establish secure connections.
On the other hand, a self-signed certificate is generated by the entity itself without involving a third-party CA. Since there is no external verification, self-signed certificates are not inherently trusted by browsers or applications. Users may see warnings when accessing a website with a self-signed certificate, as there is no guarantee of the certificate’s authenticity.
Digital Signature
A digital signature is a cryptographic mechanism used to verify the authenticity and integrity of digital documents or messages. It serves a similar purpose to a handwritten signature, but in the digital realm.
The key features of a digital signature are:
-
Authentication - The digital signature allows the recipient to verify the identity of the signer. It ensures that the message or document originated from the claimed sender.
-
Integrity - The digital signature ensures that the content of the message or document has not been altered since it was signed. Any tampering will be detected.
-
Non-repudiation - The digital signature provides proof of the origin of the message, preventing the signer from denying that they signed it.
The process works as follows:
- The signer uses their private cryptographic key to create a digital signature on the document or message.
- The recipient uses the signer’s public key to verify the signature, confirming the identity of the signer and the integrity of the content.
Digital signatures rely on public-key cryptography, where each user has a public key that can be shared, and a private key that is kept secret. The private key is used to create the digital signature, while the public key is used to verify it.
Digital signatures are widely used in various applications such as email, financial transactions, software distribution, and legal contracts to ensure secure and trusted digital communications.
Secure Socket Layer
SSL (Secure Sockets Layer) is a security protocol that provides encryption and authentication for secure communication over the internet. It is the predecessor to the modern TLS (Transport Layer Security) protocol, which has largely replaced it. It uses RSA asymetric (public key) encryption to encrypt data transferred over SSL connections.
The main functions of SSL/TLS are:
-
Encryption:
- SSL/TLS encrypts the data transmitted between a client (e.g., a web browser) and a server (e.g., a web server) to protect it from eavesdropping and tampering.
- This ensures that the data remains confidential and cannot be intercepted by third parties.
-
Authentication:
- SSL/TLS allows the client to verify the identity of the server it is communicating with.
- This is typically done through the server’s digital certificate, which is issued by a trusted Certificate Authority (CA).
- The client can verify the certificate to ensure it is valid and belongs to the expected server.
-
Integrity:
- SSL/TLS ensures that the data transmitted between the client and server has not been modified in transit.
- This is achieved through the use of message authentication codes (MACs) or digital signatures.
The SSL/TLS protocol works by establishing a secure, encrypted connection between the client and server. This process involves the following steps:
- Handshake: The client and server negotiate the encryption algorithms and exchange cryptographic keys to establish a secure connection.
- Encryption: Once the secure connection is established, all data transmitted between the client and server is encrypted using the negotiated algorithms.
- Authentication: The server’s digital certificate is verified by the client to ensure the server’s identity.
SSL/TLS is widely used in various applications, such as web browsing (HTTPS), email (SMTPS, IMAPS), and other secure communication protocols. It is an essential component of secure internet communication and helps protect against various security threats, such as eavesdropping, man-in-the-middle attacks, and data tampering.
Transport Layer Security
TLS (Transport Layer Security) is a security protocol that provides encryption, authentication, and data integrity for secure communication over the internet. It is the successor to the older SSL (Secure Sockets Layer) protocol. It uses RSA algorithm with 1024 and 2048 bit strengths.
The main functions of TLS are:
-
Encryption:
- TLS encrypts the data transmitted between a client (e.g., a web browser) and a server (e.g., a web server) to protect it from eavesdropping and tampering.
- This ensures that the data remains confidential and cannot be intercepted by third parties.
-
Authentication:
- TLS allows the client to verify the identity of the server it is communicating with.
- This is typically done through the server’s digital certificate, which is issued by a trusted Certificate Authority (CA).
- The client can verify the certificate to ensure it is valid and belongs to the expected server.
- TLS also supports mutual authentication, where the client can authenticate itself to the server as well.
-
Integrity:
- TLS ensures that the data transmitted between the client and server has not been modified in transit.
- This is achieved through the use of message authentication codes (MACs) or digital signatures.
The TLS protocol works by establishing a secure, encrypted connection between the client and server. This process involves the following steps:
- Handshake: The client and server negotiate the encryption algorithms, exchange cryptographic keys, and authenticate each other to establish a secure connection.
- Encryption: Once the secure connection is established, all data transmitted between the client and server is encrypted using the negotiated algorithms.
- Authentication: The server’s digital certificate is verified by the client to ensure the server’s identity. In mutual authentication, the client’s certificate is also verified by the server.
TLS is widely used in various applications, such as web browsing (HTTPS), email (SMTPS, IMAPS), and other secure communication protocols. It is an essential component of secure internet communication and helps protect against various security threats, such as eavesdropping, man-in-the-middle attacks, and data tampering.
TLS has evolved over time, with the latest version being TLS 1.3, which offers improved security and performance compared to earlier versions.
Pretty Good Privacy (PGP)
Pretty Good Privacy (PGP) is a data encryption and decryption computer program that provides cryptographic privacy and authentication for data communication. It is widely used for email encryption and digital signatures.
The key features of PGP are:
-
Encryption:
- PGP uses a combination of symmetric-key cryptography (e.g., AES) and public-key cryptography (e.g., RSA) to encrypt and decrypt data.
- This allows for secure communication between parties who may not have previously shared a secret key.
-
Authentication:
- PGP uses digital signatures to verify the identity of the sender and the integrity of the message.
- The sender’s private key is used to create the digital signature, and the recipient uses the sender’s public key to verify the signature.
-
Key Management:
- PGP uses a web of trust model for key management, where users can digitally sign each other’s public keys to vouch for their authenticity.
- This allows users to establish trust in the public keys of others without relying on a central authority.
The PGP workflow typically involves the following steps:
- Key Generation: Users generate their own public and private key pairs.
- Key Exchange: Users exchange their public keys with the people they want to communicate with securely.
- Encryption: The sender uses the recipient’s public key to encrypt the message.
- Decryption: The recipient uses their private key to decrypt the message.
- Signing: The sender can sign the message with their private key to provide authentication.
- Verification: The recipient can verify the signature using the sender’s public key.
PGP is widely used in email communication, file encryption, and secure messaging applications. It is an important tool for maintaining privacy and security in digital communications, especially in situations where sensitive information needs to be shared.
PGP was originally developed by Phil Zimmermann in 1991 and has since been adopted by various organizations and individuals around the world. It is an open-source project, and there are several implementations and variations of the PGP software available.
Birthday Attack
A birthday attack is a type of cryptographic attack that exploits the mathematics behind the birthday paradox. The birthday paradox states that in a group of just 23 people, there is a greater than 50% chance that two people will share the same birthday. This probability increases as the group size grows.
In the context of cryptography, a birthday attack involves finding a collision in a hash function. A hash function is a mathematical algorithm that takes an input (or message) and produces a fixed-size string of bytes, typically a hash value. The goal of a birthday attack is to find two different inputs that produce the same hash value.
By generating a large number of random inputs and calculating their hash values, an attacker can exploit the birthday paradox to increase the likelihood of finding a collision. Once a collision is found, the attacker can potentially use it to compromise the security of a system that relies on the integrity of the hash function.
To mitigate the risk of birthday attacks, cryptographic protocols and systems often use hash functions with larger output sizes and employ techniques such as salting and key stretching to increase the complexity of generating collisions. Additionally, regularly updating cryptographic algorithms and protocols can help defend against potential vulnerabilities associated with birthday attacks.
Tools for Encrypting/Decrypting files/folders
Veracrypt: Create a volume with veracrypt and lock it. Save files and folders in that volume. HashCalc: When a file is created, using the hashcalc app, generate the hash values. When the file is modified run the hashcalc again. It will display different hash values this time. Cryptoforge: Encrypt/Decrypt files.
Your inbox needs more DevOps articles.
Subscribe to get our latest content by email.