;;; cmac.lisp -- The CMAC algorithm from NIST 800-38B. (in-package :crypto) (defclass cmac ()   ((cipher :reader cmac-cipher :initarg :cipher)    (subkey1 :reader cmac-subkey1 :initarg :subkey1             :type (simple-array (unsigned-byte 8) (*)))    (subkey2 :reader cmac-subkey2 :initarg :subkey2             :type (simple-array (unsigned-byte 8) (*)))    (buffer :reader cmac-buffer :initarg :buffer            :type (simple-array (unsigned-byte 8) (*)))    (buffer-index :accessor cmac-buffer-index :initform 0 :type index))) (defun make-cmac (key cipher-name)   (declare (type (simple-array (unsigned-byte 8) (*)) key))   (let* ((cipher (make-cipher cipher-name :key key :mode :ecb))          (block-length (block-length cipher-name))          (L (make-array block-length :element-type '(unsigned-byte 8)                         :initial-element 0)))     (encrypt-in-place cipher L)     (flet ((gen-subkey (b)              (let* ((n-bits (* block-length 8))                     (k (integer-to-octets                         (ldb (byte n-bits 0) (ash (octets-to-integer b) 1))                         :n-bits n-bits)))                (when (logbitp 7 (aref b 0))                  (setf (aref k (1- block-length))                        (logxor (ecase block-length                                  (16 #x87)                                  (8 #x1b))                                (aref k (1- block-length)))))                k)))       (let ((L.u (gen-subkey L)))         (make-instance 'cmac                        :cipher cipher                        :subkey1 L.u                        :subkey2 (gen-subkey L.u)                        :buffer (make-array block-length                                            :element-type '(unsigned-byte 8)                                            :initial-element 0)))))) (defun update-cmac (cmac sequence                     &key (start 0) end)   (declare (type (simple-array (unsigned-byte 8) (*)) sequence))   (declare (type index start))   (declare (type (or index null) end))   (do ((end (or end (length sequence)))        (buffer (cmac-buffer cmac))        (length (length (cmac-buffer cmac)))        (i start (1+ i)))       ((>= i end) cmac)     (declare (type (simple-array (unsigned-byte 8) (*)) buffer))     (when (= length (cmac-buffer-index cmac))       (setf (cmac-buffer-index cmac) 0)       (encrypt-in-place (cmac-cipher cmac) buffer))     (setf (aref buffer (cmac-buffer-index cmac))           (logxor (aref buffer (cmac-buffer-index cmac)) (aref sequence i)))     (incf (cmac-buffer-index cmac)))) (defun cmac-digest (cmac)   (let* ((block-length (length (cmac-buffer cmac)))          (x (copy-seq (cmac-buffer cmac)))          (L (cond               ((= block-length (cmac-buffer-index cmac))                (cmac-subkey1 cmac))               (t                (setf (aref x (cmac-buffer-index cmac))                      (logxor (aref x (cmac-buffer-index cmac)) #x80))                (cmac-subkey2 cmac)))))     (xor-block block-length L x 0 x 0)     (encrypt-in-place (cmac-cipher cmac) x)     x))