Just default CPA 
```import requests as rimport sysimport reimport base64
URL = "http://167.71.246.232:8080/crypto.php"flag = ''b = 16data = 'a'*15
while True:
    d = {'text_to_encrypt': data, 'do_encrypt':'Encrypt'}
    block = r.post(URL, data=d).text    block = re.search(r'(.*?)', block).group(1)
    base64_bytes = block.encode('ascii')    block = base64.b64decode(base64_bytes)
    for i in range(0x20, 0x80):        if chr(i) in '&#': continue        d = {'text_to_encrypt': data+flag+chr(i), 'do_encrypt':'Encrypt'}
        resp = r.post(URL, data=d).text        resp = re.search(r'(.*?)', resp).group(1)
        base64_bytes = resp.encode('ascii')        resp = base64.b64decode(base64_bytes)
        sys.stdout.write('\r'+flag+chr(i))        sys.stdout.flush()
        if block[:b] == resp[:b]:            data = data[1:]            flag += chr(i)            if len(flag) == 16:                b += 16                data = 'a'*15            break    else:        print "\r" + flag + " \nDONE"        break
```
> flag{b4d_bl0cks_for_g0nks}