diff --git a/cryptography_s_des_exploring/sdes/blocks.py b/cryptography_s_des_exploring/sdes/blocks.py
new file mode 100644
index 0000000..7931b23
--- /dev/null
+++ b/cryptography_s_des_exploring/sdes/blocks.py
@@ -0,0 +1,46 @@
+"""
+Encoding a message to the 8-bits blocks.
+Decoding a message from the 8-bits blocks.
+"""
+
+import base64
+
+
+def encode(message: str):
+    """
+    Encode the UTF-8 string into base64 and converts bytes to a list which element represent a byte in a binary.
+    """
+
+    encoded = base64.b64encode(message.encode('utf-8'))
+    return map(lambda c: format(c, '08b'), encoded)
+
+
+def decode(message: list):
+    """
+    Decode the list of binary string into bytes to decode this with base64 to get the UTF-8 string.
+    """
+
+    decoded_bytes = bytes(map(lambda c: int(c, 2), message))
+
+    return base64.b64decode(decoded_bytes).decode('utf-8')
+
+
+def encode_bytes(byte_list: list):
+    """
+    Encode the UTF-8 string into base64 and converts bytes to a list which element represent a byte in a binary.
+    """
+
+    byte_list = [int(b, 2) for b in byte_list]
+    byte_data = bytes(byte_list)
+    return base64.b64encode(byte_data)
+
+
+def decode_bytes(message: str):
+    """
+    Decode the list of binary string into bytes to decode this with base64 to get the UTF-8 string.
+    """
+
+    decoded = base64.b64decode(message)
+    byte_list = list(decoded)
+    return map(lambda b: format(b, '08b'), byte_list)
+
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/sdes/__init__.py b/tests/sdes/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/sdes/test_blocks.py b/tests/sdes/test_blocks.py
new file mode 100644
index 0000000..ca0f441
--- /dev/null
+++ b/tests/sdes/test_blocks.py
@@ -0,0 +1,67 @@
+import pytest
+from cryptography_s_des_exploring.sdes.blocks import encode, decode, encode_bytes, decode_bytes
+
+
+@pytest.mark.parametrize("message, expected_message", [
+    # ab -> b'YWI='
+    ('ab', ['01011001', '01010111', '01001001', '00111101']),
+
+    # bc -> b'YmM='
+    ('bc', ['01011001', '01101101', '01001101', '00111101']),
+
+    # абвґд -> b'0LDQsdCy0pHQtA=='
+    ('абвґд', ['00110000', '01001100', '01000100', '01010001', '01110011',
+               '01100100', '01000011', '01111001', '00110000', '01110000',
+               '01001000', '01010001', '01110100', '01000001', '00111101',
+               '00111101']),
+
+    # їґєі -> b'0ZfSkdGU0ZY='
+    ('їґєі', ['00110000', '01011010', '01100110', '01010011', '01101011',
+              '01100100', '01000111', '01010101', '00110000', '01011010',
+              '01011001', '00111101']),
+])
+def test_encode(message, expected_message):
+    result = list(encode(message))
+    assert expected_message == result
+
+
+@pytest.mark.parametrize("expected_message, encoded_message", [
+    # ab -> b'YWI='
+    ('ab', ['01011001', '01010111', '01001001', '00111101']),
+
+    # bc -> b'YmM='
+    ('bc', ['01011001', '01101101', '01001101', '00111101']),
+
+    # абвґд -> b'0LDQsdCy0pHQtA=='
+    ('абвґд', ['00110000', '01001100', '01000100', '01010001', '01110011',
+               '01100100', '01000011', '01111001', '00110000', '01110000',
+               '01001000', '01010001', '01110100', '01000001', '00111101',
+               '00111101']),
+
+    # їґєі -> b'0ZfSkdGU0ZY='
+    ('їґєі', ['00110000', '01011010', '01100110', '01010011', '01101011',
+              '01100100', '01000111', '01010101', '00110000', '01011010',
+              '01011001', '00111101']),
+])
+def test_decode(expected_message, encoded_message):
+    result = decode(encoded_message)
+    assert expected_message == result
+
+
+@pytest.mark.parametrize("bytes, expected_message", [
+    (['01011001', '01010111', '01001001', '00111101'], b'WVdJPQ=='),
+    (['01011001', '01010111', '00000000', '00111101'], b'WVcAPQ==')
+])
+def test_encode_bytes(bytes, expected_message):
+    result = encode_bytes(bytes)
+    assert expected_message == result
+
+
+@pytest.mark.parametrize("expected_bytes, message", [
+    (['01011001', '01010111', '01001001', '00111101'], 'WVdJPQ=='),
+    (['01011001', '01010111', '00000000', '00111101'], 'WVcAPQ==')
+])
+def test_encode_bytes(expected_bytes, message):
+    result = list(decode_bytes(message))
+    assert expected_bytes == result
+