Multiple encipherment of triple-length keys

The multiple encipherment of a triple-length key (**K) using two double-length *KEKs, *KEKa, and *KEKb is defined as follows:

e*KEKa(KL) || e*KEKb(KM) || e*KEKa(KR) =
    eKEKaL(dKEKaR(eKEKaL(KL))) ||
    eKEKbL(dKEKbR(eKEKbL(KM))) ||
    eKEKaL(dKEKaR(eKEKaL(KR)))          

where:

• KL is the left 64 bits of **K
• KM is the next 64 bits of **K
• KR is the right 64 bits of **K
• KEKaL is the left 64 bits of *KEKa
• KEKaR is the right 64 bits of *KEKa
• KEKbL is the left 64 bits of *KEKb
• KEKbR is the right 64 bits of *KEKb
• || means concatenation