A non-encrypted voting receipt that identifies the votes cast by a voter creates potential for mischief, particularly if it is retained by the individual voter.  Thugs could demand to see the receipt and intimidate voters, imposing physical, economic or social harm on those who voted "incorrectly".  Also, counterfeit receipts could be utilized to falsely challange election outcomes.

Open source vote tallying software would be helpful, particularly if it runs on desktop computers.  Citizens could download the votes from the internet and execute the program to verify the outcome.  That is just one small piece of the overall need for transperancy throughout the process.  Generally, the more transparancy the better.

According to the NY Times, in the U.S. the election software is protected by trade-secret clauses that prevents third parties from checking the software to see if there any bugs or malfunctions.  The three major companies, Dibold, Election Systems & Software sand Sequoia Voting Systems all routinely include such clauses in their contracts.  Furthermore, the certification process for voting machines is also opaque.  The certification result reports are not available to the public and experts maintain that the certification process is not as thorough as it should be.

Representative Rush D. Holt, Democrat from NJ, introduced a bill last year to would require computerized voting systems to produce a voter-verified paper ballot and mandate that the software code be publicly available.  The bill has 60 co-sponsors all of whom are Democrats (note to US citizens: This is another example of why we need to elect more Democrats and fewer Republicans).

Professors at John Hopkins and Rice Universities wrote wrote a critical report saying that there is "no evidence of regorous software engineering discipline and the "cryptology, when used at all, is used incorrectly".  SAIC, a Maryland based engineering and research firm, also write a critical report recommending 17 steps 
that Maryland elections officials could take to ensure better security.