Wireless Communication Security Lecture 7

A cryptographic method that encrypts data bit by bit, using a keystream of random bits generated from a secret key.

A unique value used in the keystream generation process, ensuring each encryption is different even with the same key.

The sequence of random bits generated from a secret key and nonce. It's used to encrypt/decrypt the data stream.

A cryptographic operation combining the keystream with plaintext to produce ciphertext. This is usually achieved by XORing the bits together.

In stream ciphers, the keystream must be different for each encryption iteration. This means the key and nonce can be reused as long as the generated keystream is unique.

Stream ciphers are efficient and suitable for real-time applications like voice communication due to their ability to process data bit by bit.

Stream ciphers can be vulnerable to known-plaintext attacks if the keystream is compromised. This allows an attacker to decrypt other messages.

Stream ciphers are particularly suitable for encrypting data that is continuous, such as audio and video streams, where block ciphers would be inefficient.

In stream encryption, a nonce is a unique number used only once to generate a keystream, making each encryption session different.

Synchronous stream ciphers generate keystreams independently of previous plaintext or ciphertext. They use pseudo-random number generators and combine them with the key to create the keystream which is then XORed with the plaintext to produce the ciphertext.

Self-synchronizing stream ciphers (also known as asynchronous stream ciphers) use previous ciphertext bits to generate keystreams. They rely on a fixed size of the previous ciphertext block and a symmetric key to create the keystream block.

Stateful stream ciphers have an internal state that changes during the stream generation process. This internal state is used to keep track of the stream's progress and ensures that the stream is unique each time it is generated.

Counter-based stream ciphers do not have internal states. Instead, they use a counter that is incremented with each step to generate the keystream. This counter is often combined with a unique nonce and a key to ensure the keystream is unique for each encryption session.

A Linear Feedback Shift Register (LFSR) is a type of shift register used in stream ciphers to generate random values for the keystream. It works by taking a linear function of its previous state as input, creating a sequence of pseudo-random bits. Proper usage of LFSRs exhibits good statistical properties, but doesn't necessarily guarantee strong cryptographic properties.

LFSRs of this type produce looped bit representations of numbers through XOR operations on certain bits. These looped representations are used to generate the keystream in stream encryption.

A type of linear feedback shift register (LFSR) where the clocking of the register is controlled by the output of another LFSR, introducing non-linearity.

A combination generator combines the outputs of multiple parallel LFSRs using a nonlinear Boolean function. It aims to remove the linearity inherent in LFSRs by introducing non-linearity.

This generator utilizes three LFSRs (LFSR0, LFSR1, and LFSR2). LFSR2's output determines which of the other two LFSRs is clocked. If LFSR2 outputs a 0, LFSR0 is clocked; if it outputs a 1, LFSR1 is clocked. The output is the XOR of the last bits from LFSR0 and LFSR1.

This generator uses two LFSRs. One LFSR is clocked only if the output of the second LFSR is a 1; otherwise, it maintains its previous output. The output might also be combined with a third LFSR's regularly clocked output.

This generator uses a different approach by 'shrinking' the output sequence based on a second LFSR.

A specific type of stream cipher known for its speed and ease of implementation, commonly used in protocols like TLS and WLAN standards.

A stream cipher used in GSM cellular networks, it combines three linear feedback shift registers to generate a keystream for encryption.

A cryptographic technique that utilizes pairs of related keys, a public key, and a corresponding private key. This allows for secure communication and digital signatures without sharing the private key.

A category of cryptographic algorithms where two separate keys are used, one for encryption and the other for decryption. The public key is available to everyone, while the private key remains secret, ensuring secure communication.

Only the person with the corresponding private key can decrypt a message encrypted with the public key.

Alice uses Bob's public key to encrypt a message and sends it to Bob, who then decrypts it using his private key.

Digital signatures, TLS/SSL handshakes, cryptocurrency, and key sharing.

It eliminates the need for sharing secret keys between parties, eliminating a major vulnerability of symmetric key cryptography.

It provides evidence that the message originated from the rightful owner who possesses the private key used to decrypt it.

Asymmetric encryption algorithms utilize key sizes up to 4096 bits, leading to enhanced security for ciphers and ciphertexts.

It prevents data tampering during transmission because any alteration would render the message undecipherable using the receiver's private key.

The RSA algorithm is embedded in SSL/TLS, providing secure communications over networks. Its security is based on the difficulty of factoring large integers.