Security on the Internet is a big concern for many people. Keeping information that identifies you personally from falling into the wrong hands is important. Check for secure sites when submitting credit card information, be careful about who you give your email to and read privacy policies. This is all worthy advice.
If you are concerned about sending information (or you want to verify information came from where it says it came from) I would recommend you investigate Pretty Good Privacy. A useful piece of freeware to digitally sign and/or encrypt files (including emails).
PGP uses a system known as public key encryption. As a PGP user you would generate a “key pair” which is made up of both a public and private key. The private key should only be accessible by its owner but in order to share files etc. you need to share your public key (and you would need a copy of another user’s to send files). For mote information see PGP or PGP International.
Occasionally, I use PGP to sign emails or encrypt files. If you wish to email me using PGP my public key is given here.
other resources
Visit PGP and read this message (at PGPI) from Phil Zimmermann who invented PGP.
-----BEGIN PGP PUBLIC KEY BLOCK----- Version: PGPfreeware 7.0.3 for non-commercial use mQGiBDqqa5IRBADAhROjLw79PQfewCs4NXk+4c+QQ0UZoSS4rJSjrcg/bphP4Ypj RS+SJ/HKvdc4zilXwg58s5ipBw5NxqMMhmYAVNVO7hEaU+MaV++b5P+Gbc0XRGdx WgBQB0nEQieSgd6wgjFspTUqF2nepqKmJWiTroGBQkR8sLGO/xZ1mjDheQCg/y+h ADiSaf89MZJ9joE3hI70dCED/0n2IemzCE+kUEXphuQ3OVA3BT0MSOwZnA+71wox Kq0lCE+WSegTsOVwJiJgUEv1F4emEpwzuIY90XNw/HFXd0P4hI53cI1bB+eU9AFu eX7xKuj/oIN1tJ64TbsQgx+yXry1J8brQwKg61I56Q2XLi+5oQ4rED9vJwsdeG2o jqMZBACnWbH+fKSbtYSoJRS1tNkSGGLdpwtnl7WE2LUJZnI++mHZd9W58vpqAy33 otgjy8n+d8WsG9zo51Av/1pLOmAe0U1r4ryV+/4IAK2zDAngq+OhEQCmFuAeK4P7 ilozoiTfJ8XA+xObr+5klrldzxFJS8WvMwAgi2k2HO90adr+tLQbSm9uIEN1cm5v dyA8am9uQGN1cm5vdy5vcmc+iQBYBBARAgAYBQI6qmuSCAsDCQgHAgEKAhkBBRsD AAAAAAoJEHlMFze7ZjNBPv8AoP5LhNg7FJ6RTQfOdkw0vnW2P9s7AJ0dN3j7onft fEu+UrwOY06qcs9RsrQiSm9uIEN1cm5vdyA8am9uQG9uYWlyLmRlbW9uLmNvLnVr PokARgQQEQIABgUCOqzdvQAKCRB5TBc3u2YzQZB4AKDMR2cf25jOABdjFEJ19uIV 5v17ogCg1+rFyV+/nZbJaRQjhS8Kbp6N/vu5Ag0EOqprkhAIAPZCV7cIfwgXcqK6 1qlC8wXo+VMROU+28W65Szgg2gGnVqMU6Y9AVfPQB8bLQ6mUrfdMZIZJ+AyDvWXp F9Sh01D49Vlf3HZSTz09jdvOmeFXklnN/biudE/F/Ha8g8VHMGHOfMlm/xX5u/2R XscBqtNbno2gpXI61Brwv0YAWCvl9Ij9WE5J280gtJ3kkQc2azNsOA1FHQ98iLMc fFstjvbzySPAQ/ClWxiNjrtVjLhdONM0/XwXV0OjHRhs3jMhLLUq/zzhsSlAGBGN fISnCnLWhsQDGcgHKXrKlQzZlp+r0ApQmwJG0wg9ZqRdQZ+cfL2JSyIZJrqrol7D VekyCzsAAgIIAPYOvpLEo17mP9pk5+ptOMOEAbA53PsuY60aud24cZ59YoZWbUEk QugRvsHkDeGPVgxu90SoO4MzcNtW7FEcw/+UniMazgwv2FIpuWIw7YrsM0D0rXmm UfN8lb9P/Mwdd6zvDI3jzBlXMtv+eD02CltOvFcSR74D1mZ+NLYPuhnXvpEgyYcg EJy5uEhAM/kx/vuJkKhDmuVIgjYJteOxbVnr4WMgyMUOh5RpqmnYpE7MiDQfpudA wa2aIQu+dJCNOAmDzN6J1v3NblC0qjKENPYEdejYNayRwQhxOTNZHgiW6BFgA5Uc IcgtmLCtQ0z52Uc9ug6kNOM86ZOhwynwGISJAEwEGBECAAwFAjqqa5IFGwwAAAAA CgkQeUwXN7tmM0E6eQCg0jsYQuiw+k3k6cCQTvBCbGsvr78An0qlmaG22hmH7bPD EFVHdVJHpJw3 =BGsT -----END PGP PUBLIC KEY BLOCK-----