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TLS/SSL - How and Why

This article explains the fundamentals of TLS/SSL, detailing how they work, their critical role in securing data connectivity, and the difference between TLS and SSL. It also discusses the implications of weak ciphers, the risks associated with outdated protocols, and how these elements relate to PCI compliance. With insights into the SSL-Cipher-Check tool for assessing cipher strength, readers will gain a comprehensive understanding of best practices for safeguarding sensitive data during transmission over networks.

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TLS/SSL - How and Why

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  1. TLS/SSL - How and Why PCI Flags it but why do we care? By: MadHat Unspecific

  2. SSL – How and Why • What is TLS/SSL? • How does TLS/SSL work? • What is the difference between TLS and SSL? • What is it used for? • Weak Ciphers • How this relates to PCI • Exploitable • SSL-Cipher-Check (tool from Unspecific.com)

  3. What is TLS/SSL? • Transport Layer Security • Secure Socket Layers • Application Layer Protocols • Public/Asymmetric Key Cryptography • OSI Layer 6

  4. How does TLS/SSL work? • Encryption Protocol, Key Length, Hashing Algorithm • Authentication • Handshake • Request • Protocols Supported • Digital Certificate • Session Keys

  5. What is it used for? • Security & Data Integrity • Prevents Eavesdropping, tampering & message forgery • HTTP is most famous as HTTPS • Any layer 7 protocol, POP3, IMAP, SMTP, FTP • OpenVPN • Stunnel • Ncat (included with Nmap)

  6. Weak Ciphers • Old Protocols • SSLv2 • Key Strength • 40bit & 56bit ciphers • RC2, RC4, NULL • Weak Hash Algorithms • DES • ADH - anonymous DH cipher

  7. How this relates to PCI& Other Standards • PCI 4.1 - Use strong cryptography and security protocols such as SSL/TLS or IPSEC to safeguard sensitive cardholder data during transmission over open, public networks.

  8. Exploitable • Man in the Middle • Decryption of Communications

  9. SSL-Cipher-Check • OpenSSL binary • Checks ALL supported Ciphers • openssl ciphers • openssl s_client -$protocol -cipher $cipher -connect $host:$port • ssl_dump.logRaw openssl output

  10. SSL-Cipher-Check • $ ./ssl-cipher-check.pl : SSL Cipher Check: 1.1 : written by Lee 'MadHat' Heath (at) Unspecific.comUsage: ./ssl-cipher-check.pl [ -dvwas ] <host> [<port>]default port is 443-d Add debug info (show it all, lots of stuff)-v Verbose. Show more info about what is found-w Show only weak ciphers enabled.-a Show all ciphers, enabled or not-s Show only the STRONG ciphers enabled.

  11. References • http://en.wikipedia.org/wiki/Public-key_cryptography • http://en.wikipedia.org/wiki/Transport_Layer_Security • http://www.openssl.org/ • http://www.verisign.com/ssl/ssl-information-center/ssl-basics/index.html • http://en.wikipedia.org/wiki/OSI_model • http://www.gnu.org/software/gnutls/ • http://openvpn.net/ • http://www.stunnel.org/ • http://lasecwww.epfl.ch/memo/memo_ssl.shtml • http://www.owasp.org/index.php/Testing_for_SSL-TLS • http://www.unspecific.com/2009/02/16/ssl-cipher-check • http://www.schneier.com/paper-ssl.pdf • https://www.pcisecuritystandards.org/security_standards/download.html?id=pci_dss_v1-2.pdf

  12. Future Meetings/Talks • T-Shirt • DefCon

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