The Dancing Bear: A New Way of Composing Ciphers

This note presents a new way of composing cryptographic primitives which makes some novel combinations possible. For example, one can do threshold decryption using standard block ciphers, or using an arbitrary mix of different decryption algorithms – such as any three keys out of two AES keys, a 3DES key, an RSA key and a one-time pad. We also provide a new way to combine different types of primitive, such as encryption and signature. For example, Alice can construct a convertible signature that only Bob can verify, but which he can make world-verifiable using an AES key. We can incorporate even more exotic primitives, such as micropayments and puzzles, into compound constructs. Previously, there had been two basic ways to combine cryptographic primitives. One could either design a compound primitive, perhaps using the homomorphic properties of discrete exponentiation, or one could embed several primitives into a protocol. Neither is ideal for all applications, and both have been ...

• Type: Conference
• Year: 2004
• Where: SPW
• Authors: Ross Anderson
• Keywords: Cryptographic Primitives, Different Decryption Algorithms, SPW 2004, Standard Block Ciphers