NIST specifies two mechanisms for wrapping (encrypting) symmetric keys using another key. The first (and older, more widely supported) method requires the input be a multiple of 8 bytes long. The other allows any length input, though only up to 2**32 bytes.

These algorithms are described in NIST SP 800-38F, and RFCs 3394 and 5649.

These functions take an arbitrary 128-bit block cipher. NIST only allows these functions with AES, but any 128-bit cipher will do and some other implementations (such as in OpenSSL) do also allow other ciphers.

Use AES for best interop.