Value for a pre-shared-key (PSK). The value must be specified as a hexadecimal encoded string. The string must be 32 characters to 512 characters consisting of (0-9, a-f, A-F). This is for support of 128bit key to 2048bit key in increment of 8 bits. Setting this attribute to an empty or blank string will clear the PSK. A read of this attribute will always return empty to protect the plaintext value. Note: This is a write-only attribute.