TLS/PSK key length

Question

Is there a maximum length for the length of the key. I am using gnutls's psktool to create keys and I need to create key of the size of 128 bits. but the maximum value it lets me to use as key length is 64 Is this impossible.

Answer 1

Gnutls's psktool takes the key size in bytes, not in bits. So the maximum length is 64 bytes = 512 bits.