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parent
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commit
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# -*- coding: utf-8 -*-
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"""
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Created on Tue Jun 11 17:10:43 2019
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@author: Administrator
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"""
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import cv2
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import numpy as np
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img = cv2.imread('a.png',0)
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img1 = img.astype('float')
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def dct(m):
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m = np.float32(m)/255.0
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return cv2.dct(m)*255
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#print(dct(img1).shape)
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new_dct=dct(img1)
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after_dct=[]
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for i in range(len(new_dct)):
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for j in range(len(new_dct[0])):
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after_dct.append(int(new_dct[i][j]))
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#print(new_dct)
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#new_dct=new_dct.reshape(-1,1)
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#print(len(after_dct))
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#print(after_dct[:600])
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@ -0,0 +1,60 @@
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# -*- coding: utf-8 -*-
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"""
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Created on Mon Jun 10 17:30:40 2019
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@author: Administrator
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"""
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from Jsteg import Jsteg
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class F3(Jsteg):
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def __init__(self):
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Jsteg.__init__(self)
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def set_sequence_after_dct(self,sequence_after_dct):
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self.sequence_after_dct=sequence_after_dct
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sum_len=len(self.sequence_after_dct)
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zero_len=len([i for i in self.sequence_after_dct if i==0])
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one_len=len([i for i in self.sequence_after_dct if i in (-1,1)])
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self.available_info_len=sum_len-zero_len-one_len # 不是特别可靠
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print ("Load>> 大约可嵌入",sum_len-zero_len-int(one_len/2),'bits')
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print ("Load>> 最少可嵌入",self.available_info_len,'bits\n')
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def _write(self,index,data):
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origin=self.sequence_after_dct[index]
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if origin == 0:
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return False
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elif origin in (-1,1) and data==0:
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self.sequence_after_dct[index]=0
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return False
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lower_bit=origin%2
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if lower_bit==data:
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pass
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elif origin>0:
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self.sequence_after_dct[index]=origin-1
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elif origin<0:
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self.sequence_after_dct[index]=origin+1
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return True
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def _read(self,index):
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if self.sequence_after_dct[index] != 0:
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return self.sequence_after_dct[index]%2
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else:
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return None
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if __name__=="__main__":
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f3=F3()
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# 写
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sequence_after_dct=[-1,0,1]*100+[i for i in range(-7,500)]
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f3.set_sequence_after_dct(sequence_after_dct)
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info1=[0,1,0,1,1,0,1,0]
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f3.write(info1)
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# 读
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sequence_after_dct2=f3.get_sequence_after_dct()
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f3.set_sequence_after_dct(sequence_after_dct2)
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info2=f3.read()
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print (info2)
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# -*- coding: utf-8 -*-
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"""
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Created on Tue Jun 11 16:10:51 2019
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@author: Administrator
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"""
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from Jsteg import Jsteg
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class F4(Jsteg):
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def __init__(self):
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Jsteg.__init__(self)
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def set_sequence_after_dct(self,sequence_after_dct):
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self.sequence_after_dct=sequence_after_dct
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sum_len=len(self.sequence_after_dct)
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zero_len=len([i for i in self.sequence_after_dct if i==0])
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one_len=len([i for i in self.sequence_after_dct if i in (-1,1)])
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self.available_info_len=sum_len-zero_len-one_len # 不是特别可靠
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print ("Load>> 大约可嵌入",sum_len-zero_len-int(one_len/2),'bits')
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print ("Load>> 最少可嵌入",self.available_info_len,'bits\n')
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def _write(self,index,data):
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origin=self.sequence_after_dct[index]
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if origin == 0:
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return False
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elif origin == 1 and data==0:
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self.sequence_after_dct[index]=0
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return False
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elif origin == -1 and data==1:
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self.sequence_after_dct[index]=0
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return False
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lower_bit=origin%2
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if origin >0:
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if lower_bit!=data:
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self.sequence_after_dct[index]=origin-1
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else:
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if lower_bit==data:
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self.sequence_after_dct[index]=origin+1
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return True
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def _read(self,index):
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if self.sequence_after_dct[index] >0:
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return self.sequence_after_dct[index]%2
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elif self.sequence_after_dct[index]<0:
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return (self.sequence_after_dct[index]+1)%2
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else:
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return None
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if __name__=="__main__":
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f4=F4()
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# 写
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sequence_after_dct=[-1,0,1]*100+[i for i in range(-7,500)]
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f4.set_sequence_after_dct(sequence_after_dct)
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info1=[0,1,0,1,1,0,1,0]
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f4.write(info1)
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# 读
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sequence_after_dct2=f4.get_sequence_after_dct()
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f4.set_sequence_after_dct(sequence_after_dct2)
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info2=f4.read()
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print (info2)
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# -*- coding: utf-8 -*-
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"""
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Created on Mon Jun 10 15:26:43 2019
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@author: Administrator
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"""
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import math
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class Jsteg:
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def __init__(self):
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self.sequence_after_dct=None
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def set_sequence_after_dct(self,sequence_after_dct):
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self.sequence_after_dct=sequence_after_dct
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self.available_info_len=len([i for i in self.sequence_after_dct if i not in (-1,1,0)]) # 不是绝对可靠的
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print ("Load>> 可嵌入",self.available_info_len,'bits')
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def get_sequence_after_dct(self):
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return self.sequence_after_dct
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def write(self,info):
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"""先嵌入信息的长度，然后嵌入信息"""
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info=self._set_info_len(info)
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info_len=len(info)
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info_index=0
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im_index=0
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while True:
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if info_index>=info_len:
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break
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data=info[info_index]
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if self._write(im_index,data):
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info_index+=1
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im_index+=1
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def read(self):
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"""先读出信息的长度，然后读出信息"""
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_len,sequence_index=self._get_info_len()
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info=[]
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info_index=0
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while True:
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if info_index>=_len:
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break
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data=self._read(sequence_index)
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if data!=None:
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info.append(data)
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info_index+=1
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sequence_index+=1
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return info
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#===============================================================#
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def _set_info_len(self,info):
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l=int(math.log(self.available_info_len,2))+1
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info_len=[0]*l
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_len=len(info)
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info_len[-len(bin(_len))+2:]=[int(i) for i in bin(_len)[2:]]
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return info_len+info
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def _get_info_len(self):
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l=int(math.log(self.available_info_len,2))+1
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len_list=[]
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_l_index=0
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_seq_index=0
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while True:
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if _l_index>=l:
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break
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_d=self._read(_seq_index)
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if _d!=None:
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len_list.append(str(_d))
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_l_index+=1
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_seq_index+=1
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_len=''.join(len_list)
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_len=int(_len,2)
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return _len,_seq_index
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# 注意经过DCT会有负值，此处最低有效位的嵌入方式与空域LSB略有不同
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def _write(self,index,data):
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origin=self.sequence_after_dct[index]
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if origin in (-1,1,0):
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return False
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lower_bit=origin%2
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if lower_bit==data:
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pass
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elif origin>0:
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if (lower_bit,data) == (0,1):
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self.sequence_after_dct[index]=origin+1
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elif (lower_bit,data) == (1,0):
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self.sequence_after_dct[index]=origin-1
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elif origin<0:
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if (lower_bit,data) == (0,1):
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self.sequence_after_dct[index]=origin-1
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elif (lower_bit,data) == (1,0):
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self.sequence_after_dct[index]=origin+1
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return True
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def _read(self,index):
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if self.sequence_after_dct[index] not in (-1,1,0):
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return self.sequence_after_dct[index]%2
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else:
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return None
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'''
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import cv2
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import numpy as np
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def dct(m):
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m = np.float32(m)/255.0
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return cv2.dct(m)*255
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'''
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if __name__=="__main__":
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jsteg=Jsteg()
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# 写
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sequence_after_dct=[-1,0,1]*100+[i for i in range(-7,500)]
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#print(sequence_after_dct)
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jsteg.set_sequence_after_dct(sequence_after_dct)
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info1=[0,1,0,1,1,0,1,0]
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jsteg.write(info1)
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sequence_after_dct2=jsteg.get_sequence_after_dct()
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# 读
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jsteg.set_sequence_after_dct(sequence_after_dct2)
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info2=jsteg.read()
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print (info2)
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@ -0,0 +1 @@
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dajkhfahjkf
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@ -0,0 +1 @@
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dajkhfahjkf
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@ -0,0 +1,69 @@
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# -*- coding: utf-8 -*-
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"""
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Created on Sun May 19 12:43:26 2019
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@author: Administrator
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"""
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from PIL import Image
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def mod(x,y):
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return x%y
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def toasc(strr):
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return int(strr, 2)
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#le为所要提取的信息的长度，str1为加密载体图片的路径，str2为提取文件的保存路径
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def func(le,str1,str2):
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b=""
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im = Image.open(str1)
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lenth = le*8
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width,height = im.size[0],im.size[1]
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count = 0
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for h in range(height):
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for w in range(width):
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#获得(w,h)点像素的值
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pixel = im.getpixel((w, h))
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#此处余3，依次从R、G、B三个颜色通道获得最低位的隐藏信息
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if count%3==0:
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count+=1
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b=b+str((mod(int(pixel[0]),2)))
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if count ==lenth:
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break
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if count%3==1:
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count+=1
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b=b+str((mod(int(pixel[1]),2)))
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if count ==lenth:
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break
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if count%3==2:
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count+=1
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b=b+str((mod(int(pixel[2]),2)))
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if count ==lenth:
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break
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if count == lenth:
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break
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with open(str2,"w",encoding='utf-8') as f:
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for i in range(0,len(b),8):
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#以每8位为一组二进制，转换为十进制
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stra = toasc(b[i:i+8])
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#将转换后的十进制数视为ascii码，再转换为字符串写入到文件中
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#print((stra))
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f.write(chr(stra))
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print("完成信息提取！")
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def main():
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#文件长度
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le = 11
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#含有隐藏信息的图片
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new = "new.png"
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#信息提取出后所存放的文件
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get_info = "get_flag.txt"
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func(le,new,get_info)
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if __name__=='__main__':
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main()
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@ -0,0 +1,85 @@
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# -*- coding: utf-8 -*-
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"""
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Created on Sun May 19 11:20:05 2019
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@author: Administrator
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"""
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from PIL import Image
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def plus(string):
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#Python zfill() 方法返回指定长度的字符串，原字符串右对齐，前面填充0。
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return string.zfill(8)
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def get_key(strr):
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#获取要隐藏的文件内容
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with open(strr,"rb") as f:
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s = f.read()
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string=""
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for i in range(len(s)):
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#逐个字节将要隐藏的文件内容转换为二进制，并拼接起来
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#1.先用ord()函数将s的内容逐个转换为ascii码
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#2.使用bin()函数将十进制的ascii码转换为二进制
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#3.由于bin()函数转换二进制后，二进制字符串的前面会有"0b"来表示这个字符串是二进制形式，所以用replace()替换为空
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#4.又由于ascii码转换二进制后是七位，而正常情况下每个字符由8位二进制组成，所以使用自定义函数plus将其填充为8位
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string=string+""+plus(bin(s[i]).replace('0b',''))
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#print(string)
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return string
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def mod(x,y):
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return x%y
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#str1为载体图片路径，str2为隐写文件，str3为加密图片保存的路径
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def func(str1,str2,str3):
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im = Image.open(str1)
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#获取图片的宽和高
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width,height= im.size[0],im.size[1]
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print("width:"+str(width))
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print("height:"+str(height))
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count = 0
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#获取需要隐藏的信息
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key = get_key(str2)
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keylen = len(key)
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for h in range(height):
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for w in range(width):
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pixel = im.getpixel((w,h))
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a=pixel[0]
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b=pixel[1]
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c=pixel[2]
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if count == keylen:
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break
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#下面的操作是将信息隐藏进去
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#分别将每个像素点的RGB值余2，这样可以去掉最低位的值
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#再从需要隐藏的信息中取出一位，转换为整型
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#两值相加，就把信息隐藏起来了
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a= a-mod(a,2)+int(key[count])
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count+=1
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if count == keylen:
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im.putpixel((w,h),(a,b,c))
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break
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b =b-mod(b,2)+int(key[count])
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count+=1
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if count == keylen:
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im.putpixel((w,h),(a,b,c))
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break
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c= c-mod(c,2)+int(key[count])
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count+=1
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if count == keylen:
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im.putpixel((w,h),(a,b,c))
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break
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if count % 3 == 0:
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im.putpixel((w,h),(a,b,c))
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im.save(str3)
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def main():
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#原图
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old = "old.png"
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#处理后输出的图片路径
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new = "new.png"
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#需要隐藏的信息
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enc = "flag.txt"
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func(old,enc,new)
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if __name__=='__main__':
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main()
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Binary file not shown.
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After Width: | Height: | Size: 160 KiB |
Binary file not shown.
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After Width: | Height: | Size: 161 KiB |
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@ -0,0 +1,282 @@
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# PDF格式学习
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## PDF简介
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* PDF是Portable Document Format 的缩写，可翻译为“便携文件格式”，由Adobe System Incorporated 公司在1992年发明。
|
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|
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* PDF文件是一种编程形式的文档格式，它所有显示的内容，都是通过相应的操作符进行绘制的。
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* PDF基本显示单元包括：文字，图片，矢量图，图片
|
||||
* PDF扩展单元包括：水印，电子署名，注释，表单，多媒体，3D
|
||||
* PDF动作单元：书签，超链接（拥有动作的单元有很多个，包括电子署名，多媒体等等）
|
||||
## PDF的优点
|
||||
* 一致性：
|
||||
在所有可以打开PDF的机器上，展示的效果是完全一致，不会出现段落错乱、文字乱码这些排版问题。尤其是文档中，本身可以嵌入字体，避免了客户端没有对应字体，而导致文字显示不一致的问题。所以，在印刷行业，绝大多数用的都是PDF格式。
|
||||
* 不易修改：
|
||||
用过PDF文件的人，都会知道，对已经保存之后的PDF文件，想要进行重新排版，基本上就不可能的，这就保证了从资料源发往外界的资料，不容易被篡改。
|
||||
* 安全性：
|
||||
PDF文档可以进行加密，包括以下几种加密形式：文档打开密码，文档权限密码，文档证书密码，加密的方法包括：RC4，AES，通过加密这种形式，可以达到资料防扩散等目的。
|
||||
* 不失真：
|
||||
PDF文件中，使用了矢量图，在文件浏览时，无论放大多少倍，都不会导致使用矢量图绘制的文字，图案的失真。
|
||||
* 支持多种压缩方式：
|
||||
为了减少PDF文件的size，PDF格式支持各种压缩方式： asciihex，ascii85，lzw，runlength，ccitt，jbig2，jpeg(DCT)，jpeg2000(jpx)
|
||||
* 支持多种印刷标准：
|
||||
支持PDF-A，PDF-X
|
||||
|
||||
## PDF格式
|
||||
根据PDF官方指南，理解PDF格式可以从四个方面下手——**Objects**（对象）、**File structure**（物理文件结构）、**Document structure**（逻辑文件结构）、**Content streams**（内容流）。
|
||||
|
||||
### 对象
|
||||
|
||||
### 物理文件结构
|
||||
* 整体上分为文件头（Header）、对象集合（Body）、交叉引用表（Xref table）、文件尾（Trailer）四个部分，结构如图。修改过的PDF结构会有部分变化。
|
||||
* 未经修改
|
||||
|
||||
* 经修改
|
||||
|
||||
#### 文件头
|
||||
* 文件头是PDF文件的第一行,格式如下:
|
||||
```
|
||||
%PDF-1.7
|
||||
```
|
||||
* 这是个固定格式，表示这个PDF文件遵循的PDF规范版本，解析PDF的时候尽量支持高版本的规范，以保证支持大多数工具生成的PDF文件。1.7版本支持1.0-1.7之间的所有版本。
|
||||
|
||||
#### 对象集合
|
||||
* 这是一个PDF文件最重要的部分，文件中用到的所有对象,包括文本、图象、音乐、视频、字体、超连接、加密信息、文档结构信息等等,都在这里定义。格式如下:
|
||||
```
|
||||
2 0 obj
|
||||
...
|
||||
end obj
|
||||
```
|
||||
* 一个对象的定义包含4个部分：前面的2是**对象序号**，其用来唯一标记一个对象；0是**生成号**，按照PDF规范，如果一个PDF文件被修改，那这个数字是累加的，它和对象序号一起标记是原始对象还是修改后的对象，但是实际开发中，很少有用这种方式修改PDF的，都是重新编排对象号；obj和endobj是对象的定义范围，可以抽象的理解为这就是一个左括号和右括号；省略号部分是PDF规定的任意合法对象。
|
||||
* 可以通过R关键字来引用任何一个对象，比如要引用上面的对象，可以使用2 0 R，需要主意的是，R关键字不仅可以引用一个已经定义的对象，还可以引用一个并**不存在的对象**，而且效果就和引用了一个空对象一样。
|
||||