Possessing the Gate of Your enemies

I noticed that two references concerning blessing refer to "possessing the gate of your enemies."  Look at God blessing Abraham:

I will surely bless you, and I will surely multiply your offspring as the stars of heaven and as the sand that is on the seashore. And your offspring shall possess the gate of his enemies, (Genesis 22:17 ESV)

Now, look at Jesus commending Peter for Peter's identification of Jesus as the Christ. Jesus commends Peter and then blesses the Church:

And I tell you, you are Peter, and on this rock I will build my church, and the gates of hell shall not prevail against it. (Matthew 16:18)

Both passages talk about basically possessing the gates of their enemies. I'm not sure what it means, but it is an interesting parallel.