Counter mode encryption
Counter mode encryption generates a keystream by encrypting successive counter values with a block cipher and combines it with plaintext to produce ciphertext.
Real-World Cryptography
AES-CTR is a counter-mode construction that applies AES to successive counter values to generate a keystream or pseudorandom-looking output.
- How it is used
- Encrypts plaintext as the counter-mode component used by AES-GCM.
- How deep it goes
- Explains nonce construction, counters, keystream XOR, truncation, capacity, and nonce-reuse failure without implementation detail.
- Examples
- Uses 96-bit nonces, 32-bit counters, 16-byte blocks, keystream truncation, and repeated-nonce ciphertext comparison.
- What you can do after
- Operate AES-CTR by generating nonce-counter keystream blocks, XORing them with plaintext, and avoiding nonce reuse.
Read how Real-World Cryptography explains counter mode encryption →
Hacking Cryptography
Counter mode encrypts successive counter values with a block cipher to generate a keystream that is combined with plaintext.
- How it is used
- Uses a block cipher to produce a keystream for encrypting successive plaintext blocks.
- How deep it goes
- Defines keystream generation and plaintext combination, but does not provide implementation steps or attack analysis.
- Examples
- Uses a keystream-generation diagram to contrast stream-cipher processing with direct block-cipher ciphertext output.
- What you can do after
- Evaluate how block-cipher processing can emulate keystream-based encryption across multiple plaintext blocks.
Read how Hacking Cryptography explains counter mode encryption →
Related concepts
- stream cipherimplements · A stream cipher is an encryption algorithm that combines plaintext sequentially with a generated keystream, typically using XOR.
- Galois/Counter Modeimplemented by · Galois/Counter Mode is an authenticated-encryption mode that combines counter-mode encryption with authentication of ciphertext and associated data.
- CCMPused by · CCMP is an IEEE 802.11 wireless security protocol that combines AES counter-mode encryption with CBC-MAC-based message authentication.
- GCMPused by · GCMP is a wireless data-protection protocol that combines AES counter-mode encryption with GMAC integrity protection.
- encryptionkind of · Encryption is the cryptographic transformation of readable data into ciphertext to conceal its contents, reversible through decryption with appropriate information.
- pseudo-random number generatorproduces · A pseudorandom number generator is a deterministic computational process that uses an initial seed or internal state to produce a sequence with random-like statistical properties.
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