lib/crypto: add in-place xor cipher on CStrings

The xor operation as defined in xor_ciphers lacked a performance-aware
version on byte sequences.

This commit adds a fast version to perform it on a CString.

Signed-off-by: Lucas Bajolet <lucas.bajolet@gmail.com>

diff --git a/lib/crypto/xor_ciphers.nit b/lib/crypto/xor_ciphers.nit
index 1c4807c..18de9fb 100644 (file)
--- a/lib/crypto/xor_ciphers.nit
+++ b/lib/crypto/xor_ciphers.nit
@@ -32,6 +32,21 @@ redef class Bytes
        end
 end
 
+redef class CString
+       # In-place XOR `self` with `key`
+       fun xor(key: CString, len: Int, key_length: Int, key_offset: nullable Int) do
+               if key_offset == null then key_offset = 0
+
+               var key_pos = key_offset % key_length
+
+               for i in [0 .. len[ do
+                       self[i] = key[key_pos] ^ self[i]
+                       key_pos += 1
+                       if key_pos >= key_length then key_pos = 0
+               end
+       end
+end
+
 # Base class to modelize cryptographic ciphers
 abstract class Cipher
 

diff --git a/tests/sav/test_inplace_xor.res b/tests/sav/test_inplace_xor.res
new file mode 100644 (file)
index 0000000..ca5e7b1
--- /dev/null
+++ b/tests/sav/test_inplace_xor.res
@@ -0,0 +1,4 @@
+QWERTyuiopasdfghjklzxcvbnm
+qwertYUIOPASDFGHJKLZXCVBNM
+qWeRtYuIoPaSdFgHjKlZxCvBnM
+QwErTyUiOpAsDfGhJkLzXcVbNm

diff --git a/tests/test_inplace_xor.nit b/tests/test_inplace_xor.nit
new file mode 100644 (file)
index 0000000..8a073f5
--- /dev/null
+++ b/tests/test_inplace_xor.nit
@@ -0,0 +1,43 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import crypto
+
+var xor_base = b"qwertyuiopasdfghjklzxcvbnm"
+var xor_base_2 = xor_base.clone
+var xor_base_3 = xor_base.clone
+var key = b" "
+var key2 = b" \x00"
+
+var key_cstr = key.items
+var xb_cstr = xor_base.items
+
+xb_cstr.xor(key_cstr, 5, 1)
+
+print xb_cstr.to_s_with_length(xor_base.length)
+
+xb_cstr.xor(key_cstr, xor_base.length, 1)
+
+print xb_cstr.to_s_with_length(xor_base.length)
+
+var xb_cstr2 = xor_base_2.items
+var xb_cstr3 = xor_base_3.items
+var key2_cstr = key2.items
+
+xb_cstr2.xor(key2_cstr, xor_base_2.length, 2, 1)
+
+xb_cstr3.xor(key2_cstr, xor_base_3.length, 2)
+
+print xb_cstr2.to_s_with_length(xor_base_2.length)
+print xb_cstr3.to_s_with_length(xor_base_3.length)