+static const ui32_t B_len = 64; // rfc 2104, Sec. 2
+
+static byte_t ipad[B_len] = {
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
+ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36
+};