MultiSwap

In cryptography, MultiSwap is a block cipher/MAC created by Microsoft in 1999 as part of its Windows Media DRM service (WMDRM). Microsoft's internal name for the algorithm is not publicly known; it was dubbed MultiSwap in a 2001 report on WMDRM under the pseudonym "Beale Screamer". The cipher has a block size of 64 bits, but the two halves are processed nearly separately. All arithmetic operations are performed mod 232. In the encryption process, each half block has added to it the output of the previous half block. Next it undergoes 5 multiplications by odd 32-bit subkeys, each followed by a swap of its 16-bit halves. Then a final subkey is added to it. As the half blocks use separate subkeys, and the multipliers are forced to be odd, the total key size is 374 bits. The name MultiSwap comes from the cipher's multiplications and swaps. WMDRM uses this algorithm only as a MAC, never for encryption. Borisov, et al. applied a multiplicative form of differential cryptanalysis to break MultiSwap.

MultiSwap
General
Designers	Microsoft
First published	April 1999
Cipher detail
Key sizes	374 bits
Block sizes	64 bits
Best public cryptanalysis
The differential cryptanalysis of Borisov, et al. requires about 2¹³ chosen plaintexts or about 2²² known plaintexts

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In cryptography, MultiSwap is a block cipher/MAC created by Microsoft in 1999 as part of its Windows Media DRM service (WMDRM). Microsoft's internal name for the algorithm is not publicly known; it was dubbed MultiSwap in a 2001 report on WMDRM under the pseudonym "Beale Screamer".

The cipher has a block size of 64 bits, but the two halves are processed nearly separately. All arithmetic operations are performed mod 2³². In the encryption process, each half block has added to it the output of the previous half block. Next it undergoes 5 multiplications by odd 32-bit subkeys, each followed by a swap of its 16-bit halves. Then a final subkey is added to it. As the half blocks use separate subkeys, and the multipliers are forced to be odd, the total key size is 374 bits. The name MultiSwap comes from the cipher's multiplications and swaps. WMDRM uses this algorithm only as a MAC, never for encryption.

Borisov, et al. applied a multiplicative form of differential cryptanalysis to break MultiSwap.

References

[edit]

Beale Screamer (18 October 2001). "Microsoft's Digital Rights Management Scheme – Technical Details". Retrieved 20 September 2007.
Nikita Borisov, Monica Chew, Rob Johnson, David Wagner. "Cryptanalysis of MultiSwap". Archived from the original on 5 March 2016. Retrieved 9 October 2010.{{cite web}}: CS1 maint: multiple names: authors list (link)
Borisov, Chew, Johnson, Wagner (February 2002). Multiplicative Differentials (PDF/PostScript). 9th International Workshop on Fast Software Encryption (FSE '02). Leuven: Springer-Verlag. pp. 17–33. Retrieved 3 January 2007.{{cite conference}}: CS1 maint: multiple names: authors list (link)

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 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
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