Multiple decipherment of triple-length keys

The multiple decipherment of an encrypted triple-length key **Y = e*KEKa(KL) || e*KEKb(KM) || e*KEKa(KR), using two double-length *KEKs, *KEKa, and *KEKb, is defined as follows:

d*KEKa(YL) || d*KEKb(YM) || d*KEKa(YR)
   = dKEKaL(eKEKaR(dKEKaL(YL))) ||
     dKEKbL(eKEKbR(dKEKbL(YM))) ||
     dKEKaL(eKEKaR(dKEKaL(YR)))
   = d*KEKa(e*KEKa(KL)) ||
     d*KEKb(e*KEKb(KM)) ||
     d*KEKa(e*KEKa(KR))
   = **K
 

where:

• YL is the left 64 bits of **Y
• YM is the next 64 bits of **Y
• YR is the right 64 bits of **Y
• 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