什麼是Choesn ciphertext attack??
Chosen ciphertext attack is a scenaioa in which the attacker ha sthe ability to choose ciphertexts Ci and to view their corresponding decryptions--plaintexts Pi . It is essentially the same scenario as a chosen plaintext attact but applied to a descryption function, instead of encryption function.
The OFB mode transforms a block cipher into a symchronous stream cipher. The mode uses only the encryption operation of the block cipher. It consists of finite state machine, which is initialzed with an n-bit initial value or s0= IV. The state is encrypted and encryption result is used as key stream and fed back to the state.
Please see as below:
Davies, D. W. and W. L. Price (1989). Security for Computer Networks. An Introduction to Data Security in Teleprocessing and Electronic Funds Transfer ( 2nd ed.). Wiley, New York.
FIPS 81 (1980). 'DES modes of operation.' Federal Information Processing Standard (FIPS), Publication 81. National Bureau of Standards, US Department of Commerce, Washington, DC.
Flajolet, P. and A. M. Odlyzko (1999). 'Random mapping statistic.' Advances in Cryptology---EUROCRYPT '99, Lecture Notes in Computer Science, Vol. 1592, ed. J. Stern. Springer-Verlag, Birlin, pp. 329-354.
Encyclopedia of Cryptography and Security