1. A computer-implemented method, comprising: receiving, by an encoder device, a portion of plaintext, a key, and two or more keystreams, the keystreams previously generated by a block cipher encryption module of the encoder device as part of encryption of two or more other portions of the plaintext, wherein the key is a secret parameter that is at least one of created by an endpoint using the encoder device or communicated between two or more endpoints utilizing data encrypted by the encoder device; performing, by the encoder device, an exclusive-OR (XOR) operation on the two or more keystreams to create an input keystream vector; generating, by the block cipher encryption module, an updated keystream by combining the key and the input keystream vector; and producing, by the encoder device, ciphertext by combining the generated updated keystream with the received portion of the plaintext.