initial commit (b32, sha1, hmac)

src/misc.typ

@@ -0,0 +1,48 @@
+#import "utils.typ": xor-bytes
+#import "sha.typ": sha1
+
+#let _compute-block-sized-key(key, hash-func: sha1, block-size: 64) = {
+  if key.len() > block-size {
+    key = hash-func(key)
+  }
+
+  if key.len() < block-size {
+    key = bytes((0,) * (block-size - key.len())) + key
+  }
+
+  return  key
+}
+
+/// Hash-based Message Authentication Code
+/// ```example
+/// #bytes-to-hex(hmac("Key", "Hello World!"))
+/// ```
+/// -> bytes
+#let hmac(
+  /// Hashing key
+  /// -> str | bytes
+  key,
+  /// Message to hash
+  /// -> str | bytes
+  message,
+  /// Hashing function
+  /// -> function
+  hash-func: sha1,
+  /// Block size
+  /// -> number
+  block-size: 64
+) = {
+  let key = if type(key) == str {bytes(key)} else {key}
+  let message = if type(message) == str {bytes(message)} else {message}
+  assert(type(key) == bytes, message: "key must be a string or bytes, but is " + repr(type(key)))
+  assert(type(message) == bytes, message: "message must be a string or bytes, but is " + repr(type(message)))
+
+  let block-sized-key = _compute-block-sized-key(key, hash-func: hash-func, block-size: block-size)
+
+  let i-pad = bytes((0x36,) * block-size)
+  let o-pad = bytes((0x5c,) * block-size)
+  let i-key-pad = xor-bytes(key, i-pad)
+  let o-key-pad = xor-bytes(key, o-pad)
+
+  return hash-func(o-key-pad + hash-func(i-key-pad + message))
+}