Add secure generate function

3 files changed, 58 insertions, 3 deletions

diff --git a/alphanum/__init__.py b/alphanum/__init__.py
index 03894dd..3afda23 100644
--- a/alphanum/__init__.py
+++ b/alphanum/__init__.py
@@ -1,3 +1,3 @@
-from .alphanum import generate  # noqa: F401
+from .alphanum import generate, generate_s  # noqa: F401
 
 __version__ = '0.2.0dev1'
diff --git a/alphanum/alphanum.py b/alphanum/alphanum.py
index 3272f6c..7049830 100644
--- a/alphanum/alphanum.py
+++ b/alphanum/alphanum.py
@@ -1,7 +1,46 @@
 import random
+import secrets
+import string
 
-POP = 'abcdefghijklmnopqrstuvwxyz0123456789'
+POP = string.ascii_letters + string.digits
 
 
-def generate(length=1) -> str:
+def generate(length: int = 1) -> str:
+    """Generates a pseudo-random string of alphanumeric characters of the given
+    length. If no length is specified, a single character is returned.
+
+    Args:
+        length (:obj:`int`, optional): Desired string length. Defaults to 1.
+
+    Returns:
+        str: A pseudo-random alphanumeric string.
+
+    Examples:
+        >>> print(generate())
+        'G'
+        >>> print(generate(10))
+        'a93jfDjdA0'
+
+    """
     return ''.join(random.SystemRandom().choices(POP, k=length))
+
+
+def generate_s(length: int = 1) -> str:
+    """Generates a cryptographically strong random string of alphanumeric
+    characters of the given length. If no length is specified, a single
+    character is returned.
+
+    Args:
+        length (:obj:`int`, optional): Desired string length. Defaults to 1.
+
+    Returns:
+        str: A random alphanumeric string.
+
+    Examples:
+        >>> print(generate_s())
+        '5'
+        >>> print(generate_s(10))
+        't3g0Gh9Naj'
+
+    """
+    return ''.join(secrets.SystemRandom().choice(POP) for i in range(length))
diff --git a/tests/test_alphanum.py b/tests/test_alphanum.py
index fc9bc41..d567bdb 100644
--- a/tests/test_alphanum.py
+++ b/tests/test_alphanum.py
@@ -15,3 +15,19 @@ def test_subsequent_strings_differ():
     foo = alphanum.generate(10)
     bar = alphanum.generate(10)
     assert foo != bar
+
+
+def test_secure_no_string_length():
+    foo = alphanum.generate_s()
+    assert len(foo) == 1
+
+
+def test_secure_with_string_length():
+    foo = alphanum.generate_s(10)
+    assert len(foo) == 10
+
+
+def test_secure_subsequent_strings_differ():
+    foo = alphanum.generate_s(10)
+    bar = alphanum.generate_s(10)
+    assert foo != bar