Introduction to Cryptography

An attacker can choose ciphertext and observe the corresponding decrypted plaintext.

Trying every possible key until the correct one is found. The security of a cipher is directly proportional to the key size.

Exploits the probability of collisions when generating a large number of hash values.

Managing the creation, distribution, storage, and use of cryptographic keys.

Attacks that target information leakage beyond the algorithm itself, like timing or power consumption.

The process of transforming readable data into an unreadable format to protect its confidentiality, integrity, and authenticity.

A random sequence of bits generated by a special algorithm inside the cipher. It's used in stream ciphers to encrypt data bit by bit.

Ciphers that work on fixed-size blocks of data, handling each block independently, like cutting a message into pieces and locking each piece separately.

A method of encryption that uses the same key for both encrypting and decrypting data. Common examples include AES, DES, and Blowfish.

A method of encryption that uses two separate keys: one for encryption (public) and one for decryption (private). It's often used in digital signatures and public key infrastructure. Examples include RSA and ECC.

Specialized functions that convert data of any size into a fixed-length hash. It's used for verifying data integrity and authenticity. Examples include MD5 and SHA-256.

Ciphers that encrypt data bit by bit, using a keystream to create a dynamically changing code. RC4 was a popular example but has known vulnerabilities.

Attacks that try to break a cipher by analyzing only the encrypted data (ciphertext). This is the most challenging type of attack.

The hash value in bits for MD5 is 128.

Hashing involves taking a variable length input and producing a fixed length output (message digest).

The hash value in bits for SHA-1 is 160.

The hash value in bits for MD4 is 128.

IPSec Transport mode involves "end-to-end" encryption; i.e. data remains encrypted from the time it leaves a sender's device to the time it arrives at the receiver's device.

IPSec Tunnel mode involves encryption from gateway to gateway, i.e. just through the public network space.

A security analyst on a local network using monitoring tools is likely to only be able to read contents of traffic encrypted using IPSec Tunnel mode.

Chaskey is a lightweight cryptography method for signing messages (MAC). It boasts a relatively undemanding hardware implementation (only ~3,333 gates required at 1MHz clock rate) making it suitable for IoT implementation.

Chaskey has a key size of 128 bits.

A weakness of one-way hashing is that the same piece of plaintext will result in the same ciphertext unless salt is applied.

The minimum recommended key size to use with RC4 is 40 bits.

RC4 is a symmetric stream cipher with a variable key size up to a max of 2048 bits.

Data Encryption Standard (DES) has a block size of 64 bits, key size of 56 bits, and 16 rounds of substitution & transposition.

A(n) rainbow table is a collection of precomputed hash values of actual plaintext passwords used for password cracking.

Triple Data Encryption Standard (3DES) has a block size of 64 bits, key size of 112 bits, and 48 rounds of substitution & transposition.

Key sizes used with the Advanced Encryption Standard (AES) include 128, 192, or 256.

The Advanced Encryption Standard (AES) operates using 128 bit blocks.

Skipjack is a symmetric block cipher that uses a 80 bit key.

Enocoro operates with a key size of 128 bits and an initialization vector (IV) of 64 bits.

Skipjack has a block size of 64 bits.

PHOTON, SPONGENT, Lesamnta-LW, and Quark are examples of light-weight hashing algorithms.

IDEA has a block size of 64 bits, key size of 128 bits, and >17 rounds of substitution & transposition.

RSA is a partially homomorphic crypto system that leverages prime number characteristics, operates with a 1024-4096 bit variable key size, and 1 round.

Blowfish and Twofish are both symmetric block ciphers with common key sizes of 128, 192, or 256 bits.

RC5 is a symmetric block cipher that uses block sizes of 32, 64, or 128 bits and boasts a variable key size up to 2048 bits.

Quark produces a hash value of 64 or 112 bits.

The block size used with XTEA is 64 bits.

The key size used with XTEA is 128 bits.

Camelia is a symmetric block cipher.

RC6 can best be described as a symmetric block cipher.

RC2 has a block size of 64 bits and variable key size up to 128 bits. What is the minimum recommended key size to use when employing RC2? 40

The light-weight symmetric steam cipher Mickey v2 operates with a key size of 80 bits and an initialization vector (IV) variable up to 80 bits.

RC4 is a(n) symmetric stream cipher.

An entity seeking to obtain a digital certificate must generate and submit a certificate signing request (CSR) to a certificate authority to request the certificate.

MD5 is a 128-bit hash algorithm, meaning it produces a 128-bit hash value.

SHA-1 is a 160-bit hash algorithm, meaning it produces a 160-bit hash value.

IPSec Tunnel mode encrypts data between network gateways, leaving traffic between the end user device and the local network boundary unencrypted.

IPSec Transport mode encrypts data from the sender's device to the receiver's device, ensuring end-to-end security.

Chaskey is a lightweight cryptography method designed specifically for signing messages and is suitable for resource-constrained devices like IoT devices.

Salt is used in hashing to make it more difficult to crack passwords by adding a random value to the input before hashing.

The minimum recommended key size for the RC4 cipher is 40 bits.

The Advanced Encryption Standard (AES) operates using a block size of 128 bits.

Asymmetric cryptography relies on a pair of keys - one public and one private. Data encrypted with one key can only be decrypted with its corresponding pair.

Block cipher modes are techniques used in symmetric encryption to manage how data blocks are processed. They determine how the cipher handles multiple blocks.

CFB, OFB, and CTR are block cipher modes designed to mimic stream ciphers. They process data in a continuous stream rather than fixed blocks.

S-boxes are tables used in symmetric block ciphers for substitution. They replace specific input bits with different output bits during encryption.

PRESENT is a lightweight symmetric block cipher that encrypts data in blocks of 64 bits. It offers a small size, making it suitable for resource-constrained devices.

Cramer-Shoup is an enhanced public-key encryption method that incorporates one-way hashing to protect against specific attacks. It's a more secure version of El Gamal.

Homomorphic encryption allows computations to be performed on encrypted data without decryption. You can manipulate the ciphered data without knowing the plain text.

TOTP stands for Timed One Time Password. It generates unique passcodes for a specific time window based on a seed and a time value. Each code is valid for a short period.

PEM (Privacy Enhanced Mail) is an encoding scheme for X.509 certificates that supports Base64 and ASCII formats. This allows certificates to be easily exchanged via email.

NIST categorizes servers, desktops, tablets, and smartphones under the 'conventional' device spectrum for cryptography. These devices typically have more resources for encryption.

NIST categorizes embedded systems, RFID tags, and sensor networks as 'lightweight' cryptography devices. These devices have limited power and resources.

HOTP stands for Hashed One Time Password. It generates unique passcodes based on a counter value, a secret seed, and a hashing algorithm. Each code is valid for a single use.

SIMON is a lightweight symmetric block cipher specifically designed for hardware implementations. It offers fast and efficient encryption for resource-constrained devices.

SPECK, like SIMON, is a lightweight symmetric block cipher designed for software implementations. It offers fast performance and a small footprint for software applications.

A lightweight public key solution in RFID implementations that leverages elliptic curves and Diffie-Hellman for secure communication.

Hash algorithms such as Buzhash, Cityhash, Spookyhash, and Bernstein focus on speed and efficiency rather than cryptographic security.

One-time passwords (OTP) are generated dynamically based on an initial seed. Each time an OTP is generated, a unique code is created. This increases security by making each code valid for only one use.

The IPSec handshake, a part of the secure communication process, takes place on UDP Port 500 for key exchange.

The Encapsulating Security Payload protocol (ESP) is used for data confidentiality and integrity in IPSec and is identified by the protocol number 50.

The IPSec Authentication Header (AH) provides message authentication and integrity but does not encrypt the data itself. It is identified by the protocol number 51.

SSL/TLS uses a symmetric key method for establishing the secure tunnel. This allows for fast and efficient encryption of the data between the client and server. A separate signature mechanism, often utilizing a hashing method, is used for authentication and integrity.

A VPN tunnel allows a device on a private network to connect to a remote network over a public network, creating a secure and private communication channel.

Onion routing is a technique that routes data through a series of nodes, obscuring the origin and destination of the data. Each node only knows the previous and next node in the chain.

The Tor network is a peer-to-peer network where volunteers act as nodes, providing a path for data transmission. This distributes the traffic, making it difficult to identify the source or destination.

Hash algorithms like SHA-1 or MD5 create unique fingerprints (hash values) of data. This allows verifying integrity and authenticity by comparing hashes. If the data is changed, the hash will be different.

Every 10 minutes, a new block of transactions is added to the blockchain, marking a new set of transactions as complete and permanently recorded.

The blockchain is a distributed ledger that records all Bitcoin transactions. It allows the network to track how many bitcoins each user owns.

Miners are responsible for verifying and adding new blocks to the blockchain. They solve complex computational puzzles to earn rewards and validate Bitcoin transactions.

Miners receive rewards for their efforts in validating and adding new blocks to the blockchain. These rewards incentivize miners to continue securing the network.

Smart contracts are self-executing programs stored on a blockchain. They automate agreements based on predefined conditions, eliminating the need for intermediaries and ensuring trust and transparency.

Gas refers to the unit of measurement for the computational work required to execute a single Keccak-256 hash operation within the Ethereum network.

A NOBUS backdoor is a secret method that allows government agents to decrypt information, but is theoretically inaccessible to any other parties.

A measure of unpredictability in cryptographic systems. It's crucial to ensure that the encryption process is difficult to guess.

A method of encrypting data using a digital signature, which is a unique code generated using a private key. It's commonly used for secure communications and to verify the sender's identity.

A standard that defines how to encrypt and decrypt data using public-key cryptography. It's used in a wide range of applications, including SSL/TLS for secured web transactions.

A standard commonly used for password-based encryption. It helps to protect sensitive information stored in a password-protected format.

A public-key cryptographic method used for digital signatures and key exchange. It relies on the difficulty of solving the discrete logarithm problem.

A block cipher mode that encrypts data blocks independently, making it susceptible to attacks if the same block appears multiple times.

A block cipher mode that uses a counter to generate a unique keystream for each block, improving security and enabling parallel processing.

A cryptography method used for password storage in many Microsoft Windows operating systems. It's vulnerable to attacks if passwords are short and frequently used.

A cryptography method that provides a verifiable timestamp for data entities. It's used to ensure that a document or file was created or modified at a specific time.

A cryptographic method used to encrypt and decrypt data by substituting plaintext characters with other characters based on a pre-defined key.

A network security protocol that provides authentication and confidentiality for data communication. It's used to secure VPNs and other networks.

The Advanced Encryption Standard (AES) operates using 128-bit blocks, which means it encrypts data in chunks of 128 bits.

Skipjack is a symmetric block cipher that uses an 80-bit key for both encryption and decryption.

Enocoro uses a 128-bit key to scramble the data and a 64-bit initialization vector (IV) to add extra randomness to the encryption process.

Skipjack operates on data blocks of 64 bits at a time.

PHOTON, SPONGENT, Lesamnta-LW, and Quark are all examples of light-weight hashing algorithms designed for low-resource environments like IoT devices.

IDEA is a symmetric block cipher that uses a 64-bit block size, a 128-bit key, and has more than 17 rounds of complex processing to ensure strong encryption.

RSA is an asymmetric cryptography method that uses a 1024-4096 bit key and relies on prime number properties for its security.

Blowfish and Twofish are both symmetric block ciphers that use a single key for both encryption and decryption. They support key sizes of 128, 192, or 256 bits.

RC5 is a versatile symmetric block cipher that can work with blocks of 32, 64, or 128 bits. It also allows for key sizes up to 2048 bits for even greater security.

Quark produces a hash value that can be either 64 or 112 bits long, depending on the implementation.

XTEA uses a 64-bit block size when encrypting data, dividing the message into these fixed-size chunks.

XTEA utilizes a 128-bit key for encryption; this key determines the specific transformations applied to the data.

Camelia is a symmetric block cipher, meaning it uses the same key for encryption and decryption.

RC6 is a symmetric block cipher designed for speed and efficiency, focusing on encrypting data in blocks.

Mickey v2 operates with an 80-bit key and uses an initialization vector (IV) that can be up to 80 bits long.

RC4 is a symmetric stream cipher, which means it encrypts data bit by bit using a keystream.

A certificate signing request (CSR) is a formal request from an entity to a certificate authority (CA) to issue a digital certificate.

ChaCha is a symmetric stream cipher, meaning it encrypts data bit by bit using a constantly changing keystream.

RSA and DSA are both asymmetric algorithms, meaning they use two separate keys (public and private) for encryption and decryption.

Diffie-Hellman is a method for key exchange using a one-way function, allowing two parties to securely establish a shared secret key over an insecure channel.

Chaskey is a lightweight cryptography method for signing messages, ensuring that messages are authentic and haven't been tampered with during transmission.

WEP uses 40-bit RC4 for encryption, which is considered weak and vulnerable to security breaches.

An entity needs to create a pair of keys, one public and one private, to obtain a digital certificate from a Certificate Authority.

WPA employs 128-bit RC4 for encryption, offering more robust security than WEP.

Wi-Fi Protected Access 2 (WPA2) utilizes 128-bit AES for encryption, offering the highest level of security for Wi-Fi networks.

Mono-alphabetic substitution involves creating a single mapping from the original alphabet to a cipher alphabet, where each letter has a fixed replacement.

Before issuing a digital certificate to a requester, a Certificate Authority (CA) signs the certificate with its own private key, guaranteeing the certificate's authenticity.

Polyalphabetic substitution uses multiple cipher alphabets, where the mapping from the original alphabet changes depending on the position of the letter in the message.

The One-time pad, also known as the Vernam cipher, is a theoretically unbreakable encryption method where the key is used only once and is as long as the message itself.

ASCII encoding uses 8-bit values to represent characters, allowing for up to 256 unique characters.

A collision occurs when two different input values produce the same hash signature, potentially leading to security vulnerabilities.

UTF-16 encoding utilizes 16-bit values to represent characters, allowing for a wider range of characters (up to 65,536) compared to ASCII.

The light-weight symmetric stream cipher Trivium uses an 80-bit key and an 80-bit initialization vector (IV) for secure communication in devices with limited resources.

A hardware security module (HSM) is a dedicated and secure hardware device that protects and manages cryptographic keys, providing a high level of security for sensitive cryptographic operations.

A trusted platform module (TPM) is a dedicated chip within a computer system that handles hardware-level encryption, providing security features like full disk encryption for greater data protection.

HMAC is a message authentication code that combines hashing with a secret key to verify the integrity and authenticity of a message, making it harder to forge or alter.

Symmetric ciphers use the same secret key for both encryption and decryption, requiring both parties to share the key.

The binary XOR function, denoted by the symbol ^, compares two bits at a time. If the bits are different, the result is 1; if they are the same, the result is 0.

The binary AND function, denoted by the symbol &, compares two bits at a time. If both bits are 1, the result is 1; otherwise, the result is 0.

The binary OR function, denoted by the symbol |, compares two bits at a time. If at least one of the bits is 1, the result is 1; otherwise, the result is 0.

The modulo operation, denoted by the symbol %, gives you the remainder when one number is divided by another.

The two main types of symmetric ciphers are block ciphers and stream ciphers.