Does iCloud Keychain REQUIRE a Mac?

Do you have to have a Mac with Mavericks installed to be able to use iCloud Keychain on an iPhone at all?

A coworker has an iPhone 4S that he just updated to iOS 7.0.3 but he has not yet updated his Mac to Mavericks.

I have an iPhone 5 and have updated it as well as my Mac to Mavericks.

We both visited the same sites and on my phone it asked if I wanted to save the login info and on his 4S it did not ask.

We verified that we both have the same settings in Safari.

If this is true does that mean for Windows users iCloud Keychain is useless?