Puzzle Number 12: Code Breakers

In honour of recent contributions in encryption made by researchers at the University of Toronto, I thought I would finally come out with a new puzzle. In this puzzle, I have designed a relatively simple encryption algorithm (one that could easily be implemented either by hand or on a computer) and used it to encode two messages. The messages are both under the category of 'Classic science fiction film and television', but are otherwise unrelated. In order to make the puzzle somewhat more reasonable, I will point that all non-alphanumeric characters (punctuation) have been unchanged and are not involved in the encryption. Also, I only used a single case for the letters (in this case, capital) simply to make my life easier.

Message 1:
GDL4J9H3: HE5H2 G7D2BL5A6 G8FCBHD9H5F. HE1H1GH2 L8FH2 HE8H2 JCML9F3H1G CG2 HE6H4 GHL3FGE8D5D H5BHH9FDFD2GH7. D7HG G3D5JH0-MH0L5F AD7GGD9CB: HC H1LDA5CFH4 GHFL0BF3H1 BH7K KCFA3I5G, HC GH1H6B2 CIH BH6K A6D7G4H0 L2BI9 BH1K J8D5JD9A0D4NL1HD9CBG, HC K0CA7I8A8M F0C KE3H2FH8 BC AL4B E9L1G F2CBH1 K1H8G5CFH5.

Message 2:
L1 A8CBF6 HD3AH5 L4F0C D2B L1 F1L2A4L0LM G9L9F, G4L4F L3KL9M... GHL3F KL1FG

Good luck, and remember to send in your answers (or clarifying questions) to mozglubov@gmail.com.

Note: Puzzle solutions found here.