[*CTF2019]babyflash

用JPEXS反编译flash.swf得到441张黑白图片和1个mp3文件

软件下载地址：https://github.com/jindrapetrik/jpexs-decompiler/releases

右键导出图片

图片很规律，张数刚好是441=21*21，按照图片顺序，黑为1白为0，拼凑出0-1序列

图像处理脚本——识别1和0：

from PIL import Image
def aaa(s):
    image = Image.open("frames/"+str(i)+".png")
    a,b,c,d = image.getpixel((50,50))
    return a
s=''
for i in range(1,442):
    if aaa(i)==0:
        s+=''
    else:
        s+=''
print (s)

输出：

111111100110001111111100000100111001000001101110101011001011101101110100100101011101101110100101101011101100000100110001000001111111101010101111111000000001010100000000111011111011111000100110110011011101111011101101111001101111011010010001100000000011111010100000100011000000000001011100110011111111101011100110101100000101101000100010101110101011011000001101110100101101110000101110101101110110001100000101011100010010111111101101100001011

尝试一下拼一起

图片处理脚本——拼接图片：

from PIL import Image
 
length = 21
img = Image.new('RGB', (length*5, length*5))
#黑点为1白点为0
data = ""
 
for x in range(length):
    for y in range(length):
        if data[x*length+y] == '':
            for xx in range(x*5, x*5+5):
                for yy in range(y*5, y*5+5):
                    img.putpixel([xx, yy], (0,0,0))
        else:
            for xx in range(x*5, x*5+5):
                for yy in range(y*5, y*5+5):
                    img.putpixel([xx, yy], (255,255,255))
img.save('out.png')

输出：

得到前半个flag

*ctf{half_flag_&

再导出mp3文件，这个是常见套路频谱隐写，得到后半段flag

&_the_rest}

参考：https://zhuanlan.zhihu.com/p/64252028