A fast block cipher developed by Ron Rivest.
RC5 is a block cipher that is parameterized to support the following:
. A variable key length from 0 to 2048 bits
. A variable block size from 32 to 128 bits
. A variable number of rounds from 0 to 255
RC5 uses key expansion to generate a key table that is then used for encrypting plaintext and decrypting the corresponding ciphertext. RC5 encryption employs a scheme of bitwise XOR, integer addition, and data-dependent rotation operations as part of its encryption process. The security of RC5 is somewhat weakened since a 64-bit RC5 key was cracked in 2002 using idle central-processing unit (CPU) cycles on 331,000 computers across the Internet, though 128-bit RC5 keys are currently viewed as impermeable to brute-force cracking.