See here : [https://berryberry.hatenablog.jp/](https://berryberry.hatenablog.jp/entry/2022/03/27/034315)
Index.php was given.
![](https://cdn-ak.f.st-hatena.com/images/fotolife/B/Berrys/20220327/20220327031820.png)
I thought that I needed to calculate for a number would result in the same hash value (=Collision). However, I found there are two equal signs and three equal signs in the php comparison operator. In the case of two equal signs, a hash value begin with "0e" is computed as a power of zero. So, it will be true if the hash value of input number begin with "0e".Now, You can find the correct input with the program below.
```import stringimport hashlib
strings = string.ascii_uppercase + string.ascii_lowercase + string.digits
def check(h):    if (h[:2] != "0e"):        return 0    for i in range(2, len(h)):        if (h[i] not in string.digits):            return 0    return 1
def make_magic(moji, cnt):    h = hashlib.sha1(moji.encode()).hexdigest()    if (check(h)):        print(moji)     if (cnt == 9):        return     for j in strings:        moji += j        make_magic(moji, cnt+1)        moji = moji[:-1]
moji = ""for i in strings:    moji += i    make_magic(moji, 0)    moji = ""```
I input a string "AAAAABzIOf" and got the FLAG.
![](https://cdn-ak.f.st-hatena.com/images/fotolife/B/Berrys/20220327/20220327031806.png)