The U.S. Department of Defense has over a million pieces of equipment that encrypt and decrypt messages for radios, telephones and computers. Over the next five years, about 70 percent of that equipment is going to be replaced. There are two main reasons for this. The big one is that new communications equipment is entering use that is not compatible with many existing encryption devices. The other reason is that many better, cheaper and faster encryption methods have recently been developed. Public key cryptography has been very popular, and effective, for millions of personal computer users since the 1990s. In the last few years, quantum cryptography, considered science fiction two decades ago, is now available for commercial, and military, use. In addition to new techniques, new software and hardware is cheaper, smaller and more reliable. 

But theres another, unspoken, reason for the mass replacement of crypto devices. Codes can be broken, and the relentless increases in computing power available makes it easier to crack codes. During World War II, the first practical computer was built for the express purpose of cracking German secret codes. After World War II, similar techniques were used to crack Soviet codes, although by the early 1950s all discussion of American government cryptanalysis was silenced. Little has been said since, although billions of dollars a year is spent on protecting American ciphers, and cracking those used by other nations. Non-government decryption efforts, often done over the web for entertainment, as well as to demonstrate scientific prowess, have become more and more successful, and spectacular. So the replacement of all this old gear apparently is also recognition that decryption efforts are getting close to making existing American military coding equipment useless. No one will say that out loud, but thats where all this appears to be going.