Cipher block chaining data obfuscation

Abstract

Techniques of decrypting encrypted content involve performing, during each cycle of a CBC mode of decrypting blocks of ciphertext included in the streaming media, an obfuscation operation prior to generating a plaintext block from the ciphertext block of that cycle. For example, when a ciphertext block from a current CBC cycle is input into a decryption key function, the user device performs an XOR operation on the output of the decryption key function and an obfuscation pad to produce an obfuscated decryption key function output. The user device then performs a XOR operation on the obfuscated decryption key function output and a ciphertext block from a previous CBC cycle to produce an obfuscated plaintext block that cannot be read by a user device. The user device may recover the actual plaintext block by performing a XOR operation on the plaintext block and the obfuscation pad.