SSL certificates

So far, we have talked about how asymmetric key pairs and symmetric keys work in PKI. But when we talk about PKI, it is the SSL certificates that come to mind. So, what is the role of the certificates?

I travel regularly between London and Seattle. When I reach Seattle-Tacoma International Airport, border security officers ask for my passport to verify my identity. They do not know me personally, but the passport I hold is issued by an authority that operates under international migration laws, and they certify that the person who owns the passport is "Dishan Francis." If they want to check its authenticity, they can confirm with the authority who issued my passport. Once they have confirmed my identity, they can also check the visa status to decide on my entry to the country.

Similarly, when looking at public-key cryptography, we know that a public key can be used by many applications and services. But how exactly can it be published, and how can...