How to downgrade iOS 6.1.3 to 6.1.2 without losing any apps or contacts?

I would like to jailbreak my iPhone. The only thing is, that I have a LOT of contacts on my phone. I want to downgrade, but I wouldnt like to lose my contacts. Preferably also apps, but those are less important. Please don't tell me that I need SHSH blobs, because I don't have them. Download them from the internet? I don't know. Please give me a tutorial.

Well if you don't have SHSH blobs you don't got SHSH blobs you updated you phone not me or apple. You can't "download shsh blobs" they are unique to your device. If your device is eligble for iOS 7 don't upgrade a untethered jailbreak for 6.1.3 will be coming soon in the coming weeks.

PS you didn't even tell me your what iphone you have so that would help me a little

PSS if you have iPhone 4S and above even if you had SHSH blobs they would be useless its only usefull on iPhone 4 and under:-)

Without SHSH you can Downgrade easily with-In 3 minutes