Add problem from zer0pts ctf

Author: sampritipanda

2020/zer0pts-2020/nibelung/solve.py

@@ -0,0 +1,49 @@
+from pwn import *
+from sage.all import *
+
+def get_matrix(proc):
+    ans = []
+    for i in range(6):
+        x = proc.recvline().strip("\n []")
+        ans.append(map(int, x.split(", ")))
+    return ans
+
+proc = remote('13.231.224.102', 3002)
+
+proc.recvline()
+
+flag = get_matrix(proc)
+p = int(proc.recvline().strip().split()[-1])
+
+print flag
+
+R = IntegerModRing(p)
+
+curr_pow = 1
+ans = Matrix(R, matrix.zero(6))
+
+for b in range(0, 512, 8):
+    print b
+    curr = [0 for i in range(36)]
+    for i in range(6):
+        for j in range(6):
+            curr[i*6 + j] = (flag[i][j] >> b) % 256
+    proc.recvuntil("> ")
+    proc.sendline("2")
+    proc.recvuntil("Data: ")
+    payload = b64e(''.join(map(chr, curr)))
+    proc.sendline(payload)
+    proc.recvline()
+    resp = Matrix(R, get_matrix(proc))
+    ans += 2**b * resp
+
+print ans
+
+sice = ''
+for i in range(6):
+    for j in range(6):
+        sice += chr(int(ans[i][j]))
+
+print sice
+
+# zer0pts{r1ng_h0m0m0rph1sm_1s_c00l}