a stand-alone KDF. type CounterKDF struct { mac CMAC } // NewCounterKDF creates a new CounterKDF with the given key. func NewCounterKDF(b *aes.Block) *CounterKDF { return &CounterKDF{mac: *NewCMAC(b)} } // DeriveKey derives a key from the given label and context. func (kdf *CounterKDF) DeriveKey(label byte, context [12]byte) [32]byte { fips140.RecordApproved() var output [32]byte var input [aes.BlockSize]byte input[2] = label copy(input[4:], context[:]) input[1] = 0x01 // i = 1 K1 := kdf.mac.MAC(input[:])...