init

generator.py

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+import wave
+import sys
+
+alphabet="abcdefghijklmnopqrstuvwxyz "
+outfile = "output.wav"
+data= []
+
+def usage():
+    print("Usage:")
+    print("python3", sys.argv[0], "<text>")
+    print("<text> may only contain a-z and spaces")
+    return
+
+if len(sys.argv) < 2 or any(map(lambda char: not char in alphabet,sys.argv[1].lower())):
+    usage()
+    exit(1)
+    
+if(len(sys.argv[1]) < 250):
+    print("WARNING: short texts may be much harder to break. You should use at least 250 characters")
+
+input = sys.argv[1].lower()
+
+print("Generating keyboard sounds for \"", input, "\"")
+
+silence = wave.open("./data/silence.wav", 'rb')
+data.append([silence.getparams(), silence.readframes(silence.getnframes())])
+data.append([silence.getparams(), silence.readframes(silence.getnframes())])
+silence.close()
+
+for char in input:
+    if(char == " "):
+        char = "spc"
+    
+    sound_file = "./data/"+char+".wav"
+    wav_data = wave.open(sound_file, 'rb')
+    data.append([wav_data.getparams(), wav_data.readframes(wav_data.getnframes())])
+    wav_data.close()
+    
+    silence = wave.open("./data/silence.wav", 'rb')
+    data.append([silence.getparams(), silence.readframes(silence.getnframes())])
+    silence.close()  
+    
+silence.close()
+
+output = wave.open(outfile, 'wb')
+output.setparams(data[0][0])
+for i in range(len(data)):
+    output.writeframes(data[i][1])
+output.close()
+
+print("Your file is at", outfile)

solver.py

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+from scipy.io import wavfile
+import sys
+samplerate, data = wavfile.read('./output.wav')
+
+if len(sys.argv) < 2:
+    print("Usage:", "python3", sys.argv[0], "<file.wav>")
+    exit(1)
+
+i = 0
+countsilent = 0
+samplefound = 0
+
+avg = []
+start = 0
+end = 0
+avg.append([0])
+
+for sample in data:
+    i+=1	
+    if(sample[1]<100):
+        countsilent += 1
+    if(countsilent > 10000 and sample[1]>100):
+        countsilent = 0
+        #print(str(i)+": sample found")
+        start = i
+        samplefound = 1
+    if(countsilent > 8000 and samplefound==1):
+        samplefound = 0
+        #print(str(i)+": sample ended")
+        end = i
+        avg[len(avg)-1]=avg[len(avg)-1]/(end-start)
+        avg.append([0])
+    if (samplefound == 1):
+        avg[len(avg)-1] += sample[1]
+        
+alphabet = "abcdefghijklmnopqr stuvwxyz"
+avgs = {}
+
+i=0
+
+res=""
+
+for arr in avg:
+    value = round(arr[0], 2)
+    #print(value)
+    if str(value) not in avgs:
+        avgs[str(value)]=alphabet[i]
+        #print(str(value), "is", alphabet[i])
+        i+=1
+    res+=avgs[str(value)]
+    
+
+print(res)
+print("\n")
+print("plug the substitution cipher into https://www.guballa.de/substitution-solver and hope it worked!")

test.sh

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+rm output.wav
+python ./generator.py "THE DAY HAD BEGUN ON A BRIGHT NOTE THE SUN FINALLY PEELED THROUGH THE RAIN FOR THE FIRST TIME IN A WEEL AND THE FLAG IS PBCTF OPEN BRACE MECHANICAL LEYBOARDS ARE LOUD CLOSE BRACE AND THE BIRDS WERE SINGING IN ITS WARMTH THERE WAS NO WAY TO ANTICIPATE WHAT WAS ABOUT TO HAPPEN"
+python ./solver.py output.wav
+read -p "Press enter to continue"