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msteg/steganalysis/MPB.py 4.95 KB
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__author__ = 'chunk'
"""
Yun Q. Shi, et al - A Markov Process Based Approach to Effective Attacking JPEG Steganography
"""

import time
import math
import numpy as np
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from .. import *
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from ...common import *
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# from numba import jit
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base_dir = '/home/hadoop/data/HeadShoulder/'


class MPB(StegBase):
    """
    Markov Process Based Steganalyasis Algo.
    """

    def __init__(self):
        StegBase.__init__(self, sample_key)
        self.model = None
        self.svm = None

    def _get_trans_prob_mat_orig(self, ciq, T=4):
        """
        Original!
        Calculate Transition Probability Matrix.

        :param ciq: jpeg DCT coeff matrix, 2-D numpy array of int16 (pre-abs)
        :param T: signed integer, usually 1~7
        :return: TPM - 3-D tensor, numpy array of size (2*T+1, 2*T+1, 4)
        """
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        ciq = np.absolute(ciq)
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        TPM = np.zeros((2 * T + 1, 2 * T + 1, 4), np.float64)
        # Fh = np.diff(ciq, axis=-1)
        # Fv = np.diff(ciq, axis=0)
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        Fh = (ciq[:-1, :-1] - ciq[:-1, 1:]).clip(-T, T)
        Fv = (ciq[:-1, :-1] - ciq[1:, :-1]).clip(-T, T)
        Fd = (ciq[:-1, :-1] - ciq[1:, 1:]).clip(-T, T)
        Fm = (ciq[:-1, 1:] - ciq[1:, :-1]).clip(-T, T)
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        Fh1 = Fh[:-1, :-1]
        Fh2 = Fh[:-1, 1:]

        Fv1 = Fv[:-1, :-1]
        Fv2 = Fv[1:, :-1]

        Fd1 = Fd[:-1, :-1]
        Fd2 = Fd[1:, 1:]

        Fm1 = Fm[:-1, 1:]
        Fm2 = Fm[1:, :-1]

        # original:(very slow!)
        for n in range(-T, T + 1):
            for m in range(-T, T + 1):
                dh = np.sum(Fh1 == m) * 1.0
                dv = np.sum(Fv1 == m) * 1.0
                dd = np.sum(Fd1 == m) * 1.0
                dm = np.sum(Fm1 == m) * 1.0

                if dh != 0:
                    TPM[m, n, 0] = np.sum(np.logical_and(Fh1 == m, Fh2 == n)) / dh

                if dv != 0:
                    TPM[m, n, 1] = np.sum(np.logical_and(Fv1 == m, Fv2 == n)) / dv

                if dd != 0:
                    TPM[m, n, 2] = np.sum(np.logical_and(Fd1 == m, Fd2 == n)) / dd

                if dm != 0:
                    TPM[m, n, 3] = np.sum(np.logical_and(Fm1 == m, Fm2 == n)) / dm

        # 1.422729s
        return TPM
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    # @jit
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    def get_trans_prob_mat(self, ciq, T=4):
        """
        Calculate Transition Probability Matrix.

        :param ciq: jpeg DCT coeff matrix, 2-D numpy array of int16 (pre-abs)
        :param T: signed integer, usually 1~7
        :return: TPM - 3-D tensor, numpy array of size (2*T+1, 2*T+1, 4)
        """
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        return self._get_trans_prob_mat_orig(ciq, T)
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        # timer = Timer()
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        # ciq = np.absolute(ciq).clip(0, T) # Fool !!!
        ciq = np.absolute(ciq)
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        TPM = np.zeros((2 * T + 1, 2 * T + 1, 4), np.float64)
        # Fh = np.diff(ciq, axis=-1)
        # Fv = np.diff(ciq, axis=0)
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        # Fh = ciq[:-1, :-1] - ciq[:-1, 1:]
        # Fv = ciq[:-1, :-1] - ciq[1:, :-1]
        # Fd = ciq[:-1, :-1] - ciq[1:, 1:]
        # Fm = ciq[:-1, 1:] - ciq[1:, :-1]

        Fh = (ciq[:-1, :-1] - ciq[:-1, 1:]).clip(-T, T)
        Fv = (ciq[:-1, :-1] - ciq[1:, :-1]).clip(-T, T)
        Fd = (ciq[:-1, :-1] - ciq[1:, 1:]).clip(-T, T)
        Fm = (ciq[:-1, 1:] - ciq[1:, :-1]).clip(-T, T)
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        Fh1 = Fh[:-1, :-1].ravel()
        Fh2 = Fh[:-1, 1:].ravel()
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        Fv1 = Fv[:-1, :-1].ravel()
        Fv2 = Fv[1:, :-1].ravel()
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        Fd1 = Fd[:-1, :-1].ravel()
        Fd2 = Fd[1:, 1:].ravel()
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        Fm1 = Fm[:-1, 1:].ravel()
        Fm2 = Fm[1:, :-1].ravel()
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        # 0.089754s
        # timer.mark()
        # TPM[Fh1.ravel(), Fh2.ravel(), 0] += 1
        # TPM[Fv1.ravel(), Fv2.ravel(), 1] += 1
        # TPM[Fd1.ravel(), Fd2.ravel(), 2] += 1
        # TPM[Fm1.ravel(), Fm2.ravel(), 3] += 1
        # timer.report()
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        # 1.459668s
        # timer.mark()
        # for i in range(len(Fh1)):
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        # TPM[Fh1[i], Fh2[i], 0] += 1
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        # for i in range(len(Fv1)):
        #     TPM[Fv1[i], Fv2[i], 1] += 1
        # for i in range(len(Fd1)):
        #     TPM[Fd1[i], Fd2[i], 2] += 1
        # for i in range(len(Fm1)):
        #     TPM[Fm1[i], Fm2[i], 3] += 1
        # timer.report()

        # 1.463982s
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        # timer.mark()
        for m, n in zip(Fh1.ravel(), Fh2.ravel()):
            TPM[m, n, 0] += 1

        for m, n in zip(Fv1.ravel(), Fv2.ravel()):
            TPM[m, n, 1] += 1

        for m, n in zip(Fd1.ravel(), Fd2.ravel()):
            TPM[m, n, 2] += 1

        for m, n in zip(Fm1.ravel(), Fm2.ravel()):
            TPM[m, n, 3] += 1
        # timer.report()

        # 0.057505s
        # timer.mark()
        for m in range(-T, T + 1):
            dh = np.sum(Fh1 == m) * 1.0
            dv = np.sum(Fv1 == m) * 1.0
            dd = np.sum(Fd1 == m) * 1.0
            dm = np.sum(Fm1 == m) * 1.0

            if dh != 0:
                TPM[m, :, 0] /= dh

            if dv != 0:
                TPM[m, :, 1] /= dv

            if dd != 0:
                TPM[m, :, 2] /= dd

            if dm != 0:
                TPM[m, :, 3] /= dm
        # timer.report()

        return TPM
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