Cuba's dual currency

Cuba has a dual currency.  Foreigners use  CUCs.  1 CUC = 1 US dollars.  When we exchange we get .87 CUC for one dollars even though it’s based on the US dollar! Guess it’s their little revenge against the US!  Better to take Canadian dollars, euros, or English pounds.  The Cuban used to use Cuban pesos in addition to using the newer CUCs.  When this dual currency started 1 CUC was worth 120 pesos and now 1 CUC is worth 24 pesos.  The goal seems to be to get the CUC to equal 1 cuban peso and then shift to CUCs for Cubans and foreigners.