Intel Cascade Cipher

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Block cipher

DesignersErnie Brickell,
Gary Graunke

Intel Cascaded Cipher
General
Designers	Ernie Brickell, Gary Graunke
Derived from	AES, Serpent
Cipher detail
Key sizes	128 bits
Block sizes	128 bits
Structure	AES-128 in counter mode supplying key material to Serpent
Rounds	10 rounds of AES, 3 (out of 32) rounds of Serpent
Best public cryptanalysis
Specifications not published

In cryptography, the Intel Cascaded Cipher is a high bandwidth block cipher, used as an optional component of the Output Content Protection DRM scheme of the Microsoft Windows Vista operating system. The cipher is based on Advanced Encryption Standard (AES) operating in counter mode, used for generating keys, and a 3-round version of Serpent for encrypting actual content.

The Cascaded Cipher has not been subject to an open peer review process. A license for using the Cascaded Cipher is required from Intel Corporation.

CTR-ECB mode

The Cascaded Cipher specifications are not currently available on the Intel web site or in academic journals. A description of the structure of the cipher appears in a US patent application. In this case, the patent application only describes the inventive steps as claimed by its inventors, and is not a specification of the cipher as it is intended to be used to protect content in Windows Vista.

There are two embodiments of the cipher described in the US patent application.

In the counter-electronic codebook mode, the Cascaded Cipher uses full strength AES-128 in counter mode to generate a secure key stream and supplies this key-stream to a reduced round Serpent in electronic codebook mode to encrypt each plaintext block. To increase performance, each inner key stream block is reused several times to encrypt multiple blocks.

CTR-CTR mode

In the counter-counter mode, the Cascaded Cipher uses full-strength AES-128 in counter mode to generate a secure key stream and supplies this key-stream to a reduced round Serpent also operating in counter mode to encrypt each plaintext block. To increase performance, each inner key stream block is reused several times to encrypt multiple blocks.

Security

In the Microsoft document "Output Content Protection and Windows Vista", it is claimed that: "The security level achieved for typical video data is estimated to be approaching that of regular AES. This assertion is being tested by Intel putting its Cascaded Cipher out to the cryptography community to get their security assessment — that is, to see if they can break it."

The security of the system requires that it is impossible to recover the currently active inner key from the output of the reduced round Serpent encrypted video stream. Furthermore, the security of this method is highly sensitive to the number of rounds used in Serpent, the mode of operation described in the patent application, and the number of times the inner key is reused.

References

"Method and apparatus for increasing the speed of cryptographic processing". US Patent Application #20060126843. Archived from the original on 2011-07-16. Retrieved 2007-01-13.
"Output Content Protection and Windows Vista" (Microsoft Word document). Microsoft. 2005-04-27. Retrieved 2007-01-13.^{[better source needed]}

v t e Block ciphers (security summary)
Common algorithms	AES Blowfish DES (internal mechanics, Triple DES) Serpent SM4 Twofish
Less common algorithms	ARIA Camellia CAST-128 GOST IDEA LEA RC5 RC6 SEED Skipjack TEA XTEA
Other algorithms	3-Way Adiantum Akelarre Anubis Ascon BaseKing BassOmatic BATON BEAR and LION CAST-256 Chiasmus CIKS-1 CIPHERUNICORN-A CIPHERUNICORN-E CLEFIA CMEA Cobra COCONUT98 Crab Cryptomeria/C2 CRYPTON CS-Cipher DEAL DES-X DFC E2 FEAL FEA-M FROG G-DES Grand Cru Hasty Pudding cipher Hierocrypt ICE IDEA NXT Intel Cascade Cipher Iraqi Kalyna KASUMI KeeLoq KHAZAD Khufu and Khafre KN-Cipher Kuznyechik Ladder-DES LOKI (97, 89/91) Lucifer M6 M8 MacGuffin Madryga MAGENTA MARS Mercy MESH MISTY1 MMB MULTI2 MultiSwap New Data Seal NewDES Nimbus NOEKEON NUSH PRESENT Prince Q QARMA RC2 REDOC Red Pike S-1 SAFER SAVILLE SC2000 SHACAL SHARK Simon Speck Spectr-H64 Square SXAL/MBAL Threefish Treyfer UES xmx XXTEA Zodiac
Design	Feistel network Key schedule Lai–Massey scheme Product cipher S-box P-box SPN Confusion and diffusion Round Avalanche effect Block size Key size Key whitening (Whitening transformation)
Attack (cryptanalysis)	Brute-force (EFF DES cracker) MITM Biclique attack 3-subset MITM attack Linear (Piling-up lemma) Differential Impossible Truncated Higher-order Differential-linear Distinguishing (Known-key) Integral/Square Boomerang Mod n Related-key Slide Rotational Side-channel Timing Power-monitoring Electromagnetic Acoustic Differential-fault XSL Interpolation Partitioning Rubber-hose Black-bag Davies Rebound Weak key Tau Chi-square Time/memory/data tradeoff
Standardization	AES process CRYPTREC NESSIE NSA Suite B CNSA
Utilization	Initialization vector Mode of operation Padding

v t e Cryptography
General	History of cryptography Outline of cryptography Classical cipher Cryptographic protocol Authentication protocol Cryptographic primitive Cryptanalysis Cryptocurrency Cryptosystem Cryptographic nonce Cryptovirology Hash function Cryptographic hash function Key derivation function Secure Hash Algorithms Digital signature Kleptography Key (cryptography) Key exchange Key generator Key schedule Key stretching Keygen Machines Cryptojacking malware Ransomware Random number generation Cryptographically secure pseudorandom number generator (CSPRNG) Pseudorandom noise (PRN) Secure channel Insecure channel Subliminal channel Encryption Decryption End-to-end encryption Harvest now, decrypt later Information-theoretic security Plaintext Codetext Ciphertext Shared secret Trapdoor function Trusted timestamping Key-based routing Onion routing Garlic routing Kademlia Mix network
Mathematics	Cryptographic hash function Block cipher Stream cipher Symmetric-key algorithm Authenticated encryption Public-key cryptography Quantum key distribution Quantum cryptography Post-quantum cryptography Message authentication code Random numbers Steganography
Category

CTR-CTR mode

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