The NSA, the original primary developer of SELinux, released the first version to the open source development community under the GNU GPL on December 22, 2000.[6] The software was merged into the mainline Linux kernel 2.6.0-test3, released on 8 August 2003. Other significant contributors include Red Hat, Network Associates, Secure Computing Corporation, Tresys Technology, and Trusted Computer Solutions.
The specific example I’m thinking of is DES. They messed with the S-boxes, and nobody at the time knew why. The assumption was that they weakened them.
However, some years later, cryptographers working in public developed differential cryptanalysis to break ciphers. Turns out, those changed S-boxes made it difficult to apply differential cryptanalysis. So it appears they actually made it stronger.
But then there’s this other wrinkle. They limited the key size to 56-bits, which even at the time was known to be too small. Computers would eventually catch up to that. Nation states would be able to break it, and eventually, well funded corporations would be able to break it. That time came in the 90s.
It appears they went both directions with that one. They gave themselves a window where they would be able to break it when few others could, including anything they had stored away over the decades.
Honestly I think it ultimately comes down to the size of the organization. Chances are the right hand doesn’t know what the left hand is doing.
I do like the direction the US is heading it. Some top brass have finally caught on that you can’t limit access to back doors.