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Getting Started With PGP

Getting Started With PGP. Digital Signature and Encryption for E-mail and Data Files. ISC/Information Security. Problem: E-mail is insecure. More like a postcard than a letter Can be read by any number of people in transit

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Getting Started With PGP

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  1. Getting Started With PGP Digital Signature and Encryption for E-mail and Data Files ISC/Information Security

  2. Problem: E-mail is insecure • More like a postcard than a letter • Can be read by any number of people in transit • If recipient’s account is compromised, may be read by unauthorized person(s) • Network sniffing may capture and reveal content to unauthorized person(s) ISC/Information Security security@isc.upenn.edu

  3. Problem: E-mail is easily forged • Current protocols date back to early 1970s • Headers, especially “From:” are ridiculously easy to forge • If sender account is compromised, may not actually have been sent by that person • How can you verify the sender’s identity? ISC/Information Security security@isc.upenn.edu

  4. Problem: Sensitive & Confidential Data on Hard Drives • Especially Laptops! • If system is compromised or stolen, lots of potential fallout: • Permanent loss of irreplaceable and/or proprietary data • Exposure of secret or sensitive information • Financial loss • Disclosure requirements • …to name just a few! ISC/Information Security security@isc.upenn.edu

  5. Problem: Sensitive & Confidential Data on Hard Drives (Cont.) • Data from deleted files can be forensically recovered • Unallocated disk space often still retains data from file that most recently occupied it • “Slack space”, i.e., allocated but not used • On Windows systems, can still have data from a deleted file • Unix/linux systems will fill this space with ‘0’s’ • Data can even be recovered from a drive that: • Has been re-formatted! • No longer runs (platters can be removed and examined) • How do you securely delete sensitive files? • DoD 5220.22-M standards • www.dss.mil/isec/nispom_0195.htm ISC/Information Security security@isc.upenn.edu

  6. Solution(?): Windows EFS • Offers “one-click” encryption of individual files and/or entire folders • Problem: Encryption removed when file copied or moved to other media, e.g. floppy disc or CD • Problem: Management of encryption/decryption keys is not “user-friendly” (more on keys in a few minutes)…lost or corrupted key may mean loss of data - FOREVER! • Problem: EFS can be circumvented if Administrator account is compromised • Problem: Windows XP/2000 ONLY… • Problem: Doesn’t deal with e-mail at all • Problem: No secure delete/wipe capability ISC/Information Security security@isc.upenn.edu

  7. Solution: PGP (“Pretty Good Privacy”) • Developed in 1991 by Phil Zimmerman • Based on public/private key pair cryptography principle developed by Whitfield Diffie • Provides highly secure, portable encryption and signature for any digital data - including e-mail • Includes secure wipe utility conforming to DoD 5220.22-M standards (3 passes or more) • Available for all versions of Windows and Mac OS • Freeware unix/linux equivalent GPG (“GNU Privacy Guard”) available ISC/Information Security security@isc.upenn.edu

  8. PGP: Drawbacks • Not all that “user friendly” • Public/private key concepts take some getting used to • Doesn’t scale well to large user groups • Requires understanding of and adherence to key maintenance standards and practices • If your private key is lost, corrupted or compromised, you have to generate a new one and start all over again ISC/Information Security security@isc.upenn.edu

  9. PGP: Licensing • Freeware Windows & Mac versions available from MIT: web.mit.edu/network/pgp.html • For personal use only! • GUI and/or command line interface • For US download and use only, due to export restrictions • In many countries, import and use of encrypting software is illegal! • Some will jail you for not providing a decryption key • Commercial Windows & Mac versions available from PGP Inc.: www.pgp.com • Generally about $50 per user license • Expect to use commercial product if needed in conjunction with your job at Penn • GPG for unix/linux available as freeware from www.gnupg.org • Also works on Mac OS X: http://macgpg.sourceforge.net/ (Thanks to Larry Macy for providing info and URL) • Most versions include “plug-ins” for popular e-mail clients, e.g. Eudora ISC/Information Security security@isc.upenn.edu

  10. PGP: How Does It Work? • Let’s start with some basics of cryptography, and the high-level mathematics underneath it • Don’t worry, there won’t be a pop quiz at the end of this presentation…this is just to give you an idea of what’s going on. ISC/Information Security security@isc.upenn.edu

  11. Some Quick Definitions • Cryptography: the art and science of encrypting and decrypting secure messages • Cryptanalysis: the art and science of breaking cryptography • Cryptology: the mathematics of cryptography and cryptanalysis • Algorithm: a mathematical function/process used for encryption, decryption and verification • Key: a string (or number) used for character-by-character encryption and decryption ISC/Information Security security@isc.upenn.edu

  12. (Digital) Keys • In computer cryptography, a key is simply a binary number of varying length, depending on the type of cryptography being used • “Symmetric” cryptography generally relies on keys of 128 bits or more (e.g. most web browser SSL sessions) • “Asymmetric” cryptography requires keys of minimum 1024-bit length (2048 is typical these days) • A properly generated key can only be cracked by “brute force” - and only then after thousands of years (even at today’s processing speeds) ISC/Information Security security@isc.upenn.edu

  13. Keys: Encoding and Decoding(A bit oversimplified) One typical way keys are used to encrypt/decrypt is by use of “exclusive-OR” (XOR) logic: • If the bit to be encrypted is the same as the corresponding key bit, the encrypted bit is 0 • If they are different, the resulting encrypted bit is 1 • Without the key, you can’t be sure what the original bit was • Simple keys like this are vulnerable to “known text” attacks TEXT KEY RESULT 0 00 0 11 1 01 1 10 ISC/Information Security security@isc.upenn.edu

  14. “Symmetric” Cryptography • Relies on both sender and recipient having identical copies of the encryption key - or access to a “third party” that can verify that both have the correct key (e.g. online “certificate authority”) • Can use relatively low key lengths • 128 bits is more or less standard • 56 bits has been cracked • Problem: secure key distribution ISC/Information Security security@isc.upenn.edu

  15. “Asymmetric” Cryptography(aka “Public/Private Key”) • Sender generates a “public/private” key pair • The “public” key can be freely given out • Published on website, in e-mail sigs, etc. • Some people put them on the back of their business cards • The “private” key is guarded at all costs • If lost, corrupted or compromised, a new pair must be generated • All your contacts must be notified and supplied with the new public key • Data encrypted to the public key can only be decrypted by the corresponding private key - and vice versa • PGP is based on “public/private” key cryptography ISC/Information Security security@isc.upenn.edu

  16. How are public/private key pairs generated? • Oversimplifying a bit again, but they are essentially based on mathematical operations involving two really, really large prime numbers • Prime numbers have been proven to have no known predictive pattern • Remember “factoring” from your 3rd grade math? • It’s easy to factor the smaller numbers into primes: 14, 24, 49, etc • Even?…divisible by 2 • Digits add up to a number divisible by 3?…then 3 is also a factor • Last digit is 5 or 0?…divisible by 5 • A LOT harder as the numbers get bigger - in fact, impossible ISC/Information Security security@isc.upenn.edu

  17. What is this number? (225964951)-1 (To write it out in decimal form would require 7,816,230 digits - at 1 digit per second, it would take more than 90 days, non-stop) ISC/Information Security security@isc.upenn.edu

  18. The (Currently) Largest Known Prime Number (225964951)-1 Source: primes.utm.edu/largest.html (A really good site for “Stupid Number Tricks”) ISC/Information Security security@isc.upenn.edu

  19. PGP Public/Private Key Pair Strength • The public key is mathematically derived from the private key • The private key relies on the “computational difficulty” of deriving the large primes used to generate it • Private key lengths of 1024 bits are probably OK, but 2048 is the accepted standard for most users • Key lengths over 2048 bits are more secure, but tend to eat up processing power • Some keys still use the RSA standard, but most keys nowadays are generated using the Diffie-Hellman standard • Even at these lengths, “known text” attacks are a danger ISC/Information Security security@isc.upenn.edu

  20. Algorithms • Used to induce “randomness” in encoded message • Helps reduce “known text” vulnerability • “Encrypting” algorithms are designed to be reversible (they have to be, don’t they?) • Some well-known ones: DES, 3DES, AES, Blowfish, RSA • “Hashing” algorithms are “one-way”, i.e., irreversible • Used to provide “signature”, or “shared secret” verification • Used for password storage on most operating systems • Well-known ones include MD5, SHA (used by PGP) ISC/Information Security security@isc.upenn.edu

  21. Example: MD5 Input Output • B026324c6904b2a9cb4b88d6d61c81d1 • 26ab0db90d72e28ad0ba1e22ee510510 • 6d7fce9fee471194aa8b5b6e47267f03 • 48a24b70a0b376535542b996af517398 • 1dcca23355272056f04fe8bf20edfce0 ISC/Information Security security@isc.upenn.edu

  22. PGP Encryption • Encrypting algorithm is applied to the data • Appropriate key is applied to the result • Private key, if encrypting your own file data • Recipient’s public key, if sending e-mail • Why not the other way around? ISC/Information Security security@isc.upenn.edu

  23. Well-known Algorithms • The best-known algorithms are used to remove patterns and predictability from encoded messages • They are not secret - in fact, they are made public and subjected to rigorous testing by mathematical peers. Proprietary algorithms are not generally accepted in public cryptographic circles. • Encryption algorithms are reversible - they have to be • Applying the key before the algorithm is pointless, because the algorithm can be reversed, leaving the key exposed to “known text” and “brute force” attacks ISC/Information Security security@isc.upenn.edu

  24. Where’s the Security? In a public/private key cryptography environment, the strength lies in the length and protection of the private key - not in the algorithm ISC/Information Security security@isc.upenn.edu

  25. Digital Signatures • Usually applied to e-mail messages to verify the sender’s identity • Sender “signs” the message with his private key • Hashing algorithm is applied as well • Hashing also provides check on message integrity • Anyone who has sender’s public key can apply it to verify sender’s identity • ONLY someone who has the corresponding private key could have sent it • Hashing also verifies that the message was not altered in transit ISC/Information Security security@isc.upenn.edu

  26. What does a “Public Key” look like? -----BEGIN PGP PUBLIC KEY BLOCK----- Version: PGP for Personal Privacy 5.0 mQGiBDcox8ARBADlerXzXx0sVf7tWg/x/FBCuZ8w2o/5kwZricxuhuFLV1htdRjG iWoHZrjmWEApYn4ikfbTtf9bqLI/rV+dxupsTrNf0dytYHv2rqmF+RlKOcmraSFH RJlFKaDQgf0rKCJrH8skif/pMUasHO15ESKU+K67K3C0BsiP1LO1jue9JwCg/64p vGo+6GmqyPP8dB5VmH3TTSUEAJy5W/rgDQCEkiu8b8KyimI9pLTmfUVr6GB11JZR FdOsZROt8ymRGd7rmLZDV/fQN+IbL79+2m6NS+DuO1zYXKnE8mwEcp7U4ggU73bH 8joGdp+D4gKX/s9uGZi1h0al1AV3xlKM2zU/M7c7MJhkPbcQbfHKNK+earE51FaW zd/MA/4/Pi6O5qLxHRdRsQYux4aG7DPcIWU0yqpQLP5/s6iYpFawSTqw1MHEyPK6 R5BcqcYL99wva9meS08M9MfYKO0Ce6x9Tf3CS7goEn94xwU9pgPgejpRlxv3SF9l cXhMfkD3T1TgR0XrGkmE+7TpsH7D5XUfrLiAwfP3RnK4DPjUbbRLSW5mb3JtYXRp b24gU2VjdXJpdHkgYXQgVW5pdmVyc2l0eSBvZiBQZW5uc3lsdmFuaWEgPHNlY3Vy aXR5QGlzYy51cGVubi5lZHU+iQB1AwUQNynGnVcYQO1Qt5kZAQFg2AL/ds5fHHmg WHVPL7VUmUv0xlVlNzaS4kz0S+57lPcghO5F1nBQxztE+ekde18D9QLC8S3S0GDw Q7CHSrIFlKQ9WTDYv3ruP48VZvJ8q5FfI81ypojMvxBePxn647Bfov84iQA/AwUQ NynGss3oSRS59y8HEQJziACfTxlMW2pKKCXr/+sk3ivFtMUzppcAn06yEouF4x5Y g0p2hWUnKIQGGIhkiQA/AwUQNynGwqDFmzsT2y3tEQIZKACg2gdxZsq8IwtTcqW5 eTQF2OJw7i0AmwbGp3hD8XO5nH+mNDFIa3I978gciQCVAwUQNynMBEZOdo0DD6gN AQHmlwP9GK8h9NI09fClK91IGcT5gFtK9q695UUDWi7+gIGTGz5yIkXbnZCUZFPm y6FLyVpUQNVyBVXD+6aMJr3flxz0Es32mY7rgYKHITz+mmyoKB6CDz2K1Ov3a6Mw W5VlN5eHPgug2imSETO4NGOdeL67LX93bYEHba1D9/2gcG909WSJAEsEEBECAAsF Ajcox8AECwMBAgAKCRCgxZs7E9st7eiaAKC6jhAEhnhnDLr5B4V2H7SYOkokHwCe OYexEbEe0Xf2VnJO6K2MmcdmN/OJAFUDBRA3KMo/hsldwo1DqVkBAZxcAf9c6OcH RkI9ohqQFV+XmYcgRuPuLL2oD6MT/ZvLu0Gp6RucDWEoA8iQFUNte73wsAkYRU0/ Zz4KoiVbtqolta+FiQA/AwUQNyjKSuyQdaHLkpQqEQKeOQCg1vU+iQp2iqHWq5on vydUxAmTU7wAn2e/uhmCjmMXjiBec+ZP0kEbScLWiQA/AwUQNym9aUXWdKqHR/jl EQKNfACg8C+pTwIM+JVnELL4GJAfWE4X33sAnRiA9UHf3SzmidVB72m0E4HaKzMs iQCVAwUQNynMAUZOdo0DD6gNAQFChgQAo69r5WRVrJAzF49CLiOIDmRAZ3eV3MYm xfMZKao2H21Tkr72CnN3y91t+XDXjJN+ciVUZuFKNmF+ubwJ9ittfzsdcuo5bUCk bvuAAtfE3utniYvgDmWNMRzAt720cTZjVTU8nvcZbUlHJx/PSqO/FrgAT0Fenmwm CJDFbu8+SA+5Ag0ENyjHwBAIAPZCV7cIfwgXcqK61qlC8wXo+VMROU+28W65Szgg 2gGnVqMU6Y9AVfPQB8bLQ6mUrfdMZIZJ+AyDvWXpF9Sh01D49Vlf3HZSTz09jdvO meFXklnN/biudE/F/Ha8g8VHMGHOfMlm/xX5u/2RXscBqtNbno2gpXI61Brwv0YA WCvl9Ij9WE5J280gtJ3kkQc2azNsOA1FHQ98iLMcfFstjvbzySPAQ/ClWxiNjrtV jLhdONM0/XwXV0OjHRhs3jMhLLUq/zzhsSlAGBGNfISnCnLWhsQDGcgHKXrKlQzZ lp+r0ApQmwJG0wg9ZqRdQZ+cfL2JSyIZJrqrol7DVekyCzsAAgIH/1pIvuZa4dPy 6Si59ZYQpuHNX1YEVRuUH5wEP0A0agNue0MOyg6liYFhx+mit7tEFe91wviQVU2v FPthdoqlP0fFlXbMg4SM65U6/NliF5qv1MHfj7TVZ5MQrKGwk0uGYBhESzGat0rU /j6v/XiU5Bzxd9r/Vr/HHSALfk9Q/8NhCXQPjaMuEym4CeVy/IbbuR472k5/O5+s P0eK7xx4eDub+Yg1TELYBoheLvf/FzmNSML/rBpL4jP+ApJbHb/SjW5f0/0dOiUi LmGHNR8zku46WTGd0eOKUoI7rRnNfFMnhFIgv4FunhI6h8alQDfBj31XkyGl40yV +f5C6O30ZYyJAD8DBRg3KMfAoMWbOxPbLe0RAkPUAKCo4sGborU5vtJ0TTh+UcV8 k5ynyACeKbCeSGtAKrYcbCtROyRzYAP/BiI= =SgNt -----END PGP PUBLIC KEY BLOCK----- • Hashed “fingerprint”: • 7D91 F6E2 8BA6 F501 1550 A904 A0C5 9B3B 13DB 2DED • (Hexadecimal) • OR - • klaxon miracle village tomorrow • obtuse paragon vapor adviser • backfield embezzle revenge alkali • ragtime resistor puppy councilman • Aztec suspicious button unify • (Keywords) ISC/Information Security security@isc.upenn.edu

  27. Public Key Distribution • Published on your personal website • Carry it around on floppy disc, CD-ROM, USB “jump drive”, etc. for people to copy • Send as e-mail attachment • Upload it to a “key server” • Print it out on a sheet of paper, along with the “fingerprint” • We’ll talk about “key signing parties” in a few minutes • Rent a billboard…well, you get the idea ISC/Information Security security@isc.upenn.edu

  28. How do I know that’s really your public key? • Generating public/private key pairs does NOT require any authentication - you can associate any name and e-mail address with a key pair you choose • To be completely certain that a given public key actually belongs to the person it claims, you need to physically verify the person’s identity and key in person • Ask for photo ID if necessary • Ask the person to read the “fingerprint”, and verify against a printed copy • Verify printed copy “fingerprint” against the electronic copy OR… ISC/Information Security security@isc.upenn.edu

  29. Is the public key “signed”? • PGP public keys can be “signed” by other private keys as “third party” verification • If the signer’s public key is one you already have, you can use it to verify the signature • If you can trust the signer’s key, you can trust the signed key ISC/Information Security security@isc.upenn.edu

  30. PGP “Web of Trust” • Built on a network of transitive trust relationships • If Tom trusts Dick… • And Dick trusts Harry… • Then Tom can trust Harry • Only in the context of identification and authentication • Doesn’t necessarily mean Tom is assured Harry is a trustworthy person…only that he really is Harry • Functions as sort of an “ad hoc Certificate Authority” • The more links in the chain, the more likely there’s a weak link somewhere along the line ISC/Information Security security@isc.upenn.edu

  31. PGP “Key Signing Parties” • Opportunity for several people to get together and exchange public keys • Held regularly by ISC Information Security • Print out your public key & fingerprint, bring with copy of your key - and your PennCard • Security will verify all identities and keys, sign and distribute them to all attendees ISC/Information Security security@isc.upenn.edu

  32. PGP “Keyring” ISC/Information Security security@isc.upenn.edu

  33. PGP Key(General Info) ISC/Information Security security@isc.upenn.edu

  34. PGP Key(SubKeys) ISC/Information Security security@isc.upenn.edu

  35. ISC/Information Security security@isc.upenn.edu

  36. ISC/Information Security security@isc.upenn.edu

  37. ISC/Information Security security@isc.upenn.edu

  38. ISC/Information Security security@isc.upenn.edu

  39. ISC/Information Security security@isc.upenn.edu

  40. ISC/Information Security security@isc.upenn.edu

  41. PGP Mail Menu Window (Mac OS X) (Windows version uses tray icon/menu) ISC/Information Security security@isc.upenn.edu

  42. Preferences(General) ISC/Information Security security@isc.upenn.edu

  43. Preferences(Files) ISC/Information Security security@isc.upenn.edu

  44. Preferences(Email) ISC/Information Security security@isc.upenn.edu

  45. Preferences (Server) ISC/Information Security security@isc.upenn.edu

  46. Questions? Comments? ISC/Information Security security@isc.upenn.edu

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