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import sys
delta_asso = [0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00,0x00, 0x00, 0x00, 0x0F, 0x00, 0x0F]
check_asso = [0x0D, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x03, 0x07, 0x0B, 0x0B, 0x0B, 0x0F]
delta_values =[(0x00), (0x00), (0x00), (0x13), (0x04), (0xBF), (0xBF), (0xB9), (0xB9), (0x00), (0x10), (0xC3), (0xBF), (0xBF), (0xB9), (0xB9)]
check_values = [(0x80), (0x80), (0x80), (0x80), (0xCF), (0xBF), (0xD5), (0xA6), (0xB5), (0x86), (0xD1), (0x80), (0xB1), (0x80), (0x91), (0x80)]
valid = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
def safechr(i):
if i < 32:
return '.'
if i > 127:
return '?'
return chr(i)
def safehex(x):
return "0x{0:2x}".format(x)
def to_signed(x):
if(x >= 128):
return x - 256
return x
def to_unsigned(x):
if(x < 0):
return x + 256
return x
def sat(x, y):
x = to_signed(x)
y = to_signed(y)
z = x + y
if(z > 127):
return 127
if(z < -128):
return to_unsigned(-128)
return to_unsigned(z)
def lookup(table, index):
print("looking up ", hex(index))
if(index >= 128):
return 0
return table[index&0xf]
def quietlookup(table, index):
if(index >= 128):
return 0
return table[index&0xf]
def process(src):
shifted = (src >> 3)%256
delta_hash = (lookup(delta_asso,src) + shifted + 1) >> 1
check_hash = (lookup(check_asso,src) + shifted + 1) >> 1
out = sat(lookup(delta_values,delta_hash), src)
chk = sat(lookup(check_values,check_hash), src)
mask = chk & 0x80
return (out, mask)
def processquiet(src):
shifted = (src >> 3)%256
delta_hash = (quietlookup(delta_asso,src) + shifted + 1) >> 1
check_hash = (quietlookup(check_asso,src) + shifted + 1) >> 1
out = sat(quietlookup(delta_values,delta_hash), src)
chk = sat(quietlookup(check_values,check_hash), src)
mask = chk & 0x80
return (out, mask)
def is_ok(i):
out, mask = processquiet(i)
if mask == 0:
return 1
return 0
def computestring():
s = ""
for i in range(256):
out, mask = processquiet(i)
if(mask == 0):
s += safechr(i)
return s
#print(computestring() + " " + str(len(computestring())))
def print_layout():
t={}
for i in range(256):
src = i
shifted = (src >> 3)%256
check_hash = (quietlookup(check_asso,src) + shifted + 1) >> 1
if check_hash not in t:
t[check_hash] = []
t[check_hash].append(i)
for check_hash in range(16):
if check_hash in t:
off = quietlookup(check_values,check_hash)
print(hex(check_hash), hex(off), end="")
print("\t", " ".join([" "+safechr(c) for c in t[check_hash]]))
else:
continue
def is_valid():
t={}
# we compute the hash for each character, we store the character in a list for each hash value
for i in range(256):
src = i
for j in range(8):
shifted = (src >> 3)%256
shifted += j << 5
check_hash = (quietlookup(check_asso,src) + shifted + 1) >> 1
if check_hash not in t:
t[check_hash] = []
t[check_hash].append(i)
# for each hash value, we check if the content of the sequence. It should be a sequence of valid characters, followed by a sequence of invalid characters, followed by a sequence of characters with the 8th bit set
for check_hash in t.keys():
if check_hash in t:
array = t[check_hash]
i = 0
while i < len(array) and valid.find(chr(array[i])) == -1:
i += 1
while i < len(array) and valid.find(chr(array[i])) != -1:
i += 1
while i < len(array) and array[i] >= 128:
i += 1
if i < len(array):
return False
else:
continue
return True
#print_layout()
print(is_valid())
#sys.exit(0)
valid = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
print("----")
def validate_top_bit():
for src in range(256):
for i in range(8):
shifted = (src >> 3)%256
shifted += i << 5
check_hash = (quietlookup(check_asso,src) + shifted + 1) >> 1
if(check_hash & 0x80 != 0):
if(src < 128 and valid.find(chr(src)) == -1):
#print("error ", hex(src), hex(check_hash))
return False
return True
def fun_adjust():
for zz in range(256):
check_asso[ord('-')&0xf] = zz
for yy in range(256):
check_asso[ord('_')&0xf] = yy
if(is_valid() and validate_top_bit()):
print("----")
print_layout()
print(is_valid())
print("found")
return
fun_adjust()
def adjust(array, start, end, check_hash):
for j in range(256):
is_ok = True
for i in range(len(array)):
valid = (sat(j,array[i])&0x80 == 0)
should_be_valid = (i>=start and i < end)
is_ok = is_ok and (valid == should_be_valid)
if(is_ok):
check_values[check_hash&0xf] = j
return
raise "unexpected"
chk = sat(quietlookup(check_values,check_hash), src)
mask = chk & 0x80
def process_explicit():
t={}
for i in range(256):
src = i
for j in range(8):
shifted = (src >> 3)%256
shifted += j << 5
check_hash = (quietlookup(check_asso,src) + shifted + 1) >> 1
if check_hash not in t:
t[check_hash] = []
t[check_hash].append(i)
for check_hash in t.keys():
if check_hash in t:
array = t[check_hash]
i = 0
while i < len(array) and valid.find(chr(array[i])) == -1:
i += 1
if i < len(array) and valid.find(chr(array[i])) != -1:
start = i
while i < len(array) and valid.find(chr(array[i])) != -1:
i += 1
end = i
adjust(array, start, end, check_hash)
else:
continue
return True
print("process")
process_explicit()
print("string")
print(computestring()+ " "+str(len(computestring())))
for c in valid:
print(c,processquiet(ord(c)))
def examine():
t={}
for i in valid:
src = ord(i)
shifted = (src >> 3)%256
check_hash = (quietlookup(delta_asso,src) + shifted + 1) >> 1
if check_hash not in t:
t[check_hash] = []
t[check_hash].append(i)
for check_hash in t.keys():
print(check_hash, t[check_hash])
return True
examine()
delta_values[10] += 1
delta_values[13] += 33
for c in valid:
print(c,processquiet(ord(c)))
def casthex(v):
if(v >= 0x80):
return "uint8_t("+"0x{:X}".format(v)+")"
return "0x{:X}".format(v)
def printme(c):
print(",".join([casthex(i) for i in c]))
print("delta_asso")
printme(delta_asso)
print("check_asso")
printme(check_asso)
print("delta_values")
printme(delta_values)
print("check_values")
printme(check_values)
def is_base64(src):
is_base64 = None
for i in range(8):
shifted = (src >> 3)%256
shifted += i << 5
check_hash = (quietlookup(check_asso,src) + shifted + 1) >> 1
chk = sat(quietlookup(check_values,check_hash), src)
this_is_base64 = chk & 0x80 == 0
if is_base64 is None:
is_base64 = this_is_base64
else:
if is_base64 != this_is_base64:
return None
return is_base64
def validate_top_bit():
for src in range(256):
for i in range(8):
shifted = (src >> 3)%256
shifted += i << 5
check_hash = (quietlookup(check_asso,src) + shifted + 1) >> 1
if(check_hash & 0x80 != 0):
if(src < 128 and valid.find(chr(src)) == -1):
#print("error ", hex(src), hex(check_hash))
return False
return True
for i in range(256):
if is_base64(i):
print(chr(i), end=",")
elif is_base64(i) is None:
print("None", hex(i), end=",")
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