The Problem
Before DES, there was no standard.
Every company, every government agency used different encryption methods. If you wanted to communicate securely, you both had to agree on which cipher to use first.
No compatibility. No trust. Chaos.
The Call for a Standard (1973)
The National Bureau of Standards (now called NIST) put out a public call:
“We need ONE encryption standard for the entire US government.”
They wanted something:
- Strong enough to protect sensitive data
- Fast enough to run on 1970s hardware
- Open for public review (no secret algorithms)
IBM’s Answer
IBM had been working on a cipher called Lucifer, designed by cryptographer Horst Feistel.
They submitted a modified version to NBS.
- Block size: 64 bits
- Key size: 128 bits
The NSA Gets Involved
Here’s where it gets controversial.
The NSA reviewed IBM’s submission and made changes:
- Reduced the key from 128 bits to 56 bits
- Modified the internal substitution tables
Nobody explained why.
People got suspicious.
Was the government weakening it so they could crack it later?
Adoption (1977)
Despite the controversy, DES became the official US encryption standard in 1977.
It spread everywhere:
- Banks used it for ATM transactions
- Businesses used it for secure communication
- It became the global encryption standard for 20 years
The Fall
56 bits seemed fine in 1977. Computers were slow.
But computers got faster. Much faster.
1998: A group called the EFF built a $250,000 machine that cracked DES in 56 hours.
1999: Combined with distributed computing, cracked in 22 hours.
56 bits was officially dead.
The Aftermath
- 3DES (Triple DES) extended DES’s life by applying it three times
- AES replaced DES as the new standard in 2001
- DES was officially retired in 2005
The Twist
Years later, researchers discovered something interesting about those NSA changes.
The modifications to the substitution tables actually made DES stronger against a technique called differential cryptanalysis, an attack that wasn’t publicly known until 1990.
The NSA knew about it decades earlier. They were strengthening DES, not weakening it.
The 56-bit key though?
That part is still suspicious.