PKI and Applications

Public Key Infrastructure and Applications Svetlin Nakov Sofia University “St. Kliment Ohridski” E-mail: [email_address] Nikolay Nedyalkov Latona Development E-mail: [email_address]

Agenda PKI Overview Digital Signatures What is it? How does it work? Digital Certificates Public Key Infrastructure PKI Components Policies Internet Security Web Security with SSL Smart Cards Email signing – S/MIME

What’s the problem? Information over the Internet is Free, Available, Unencrypted, and Untrusted. Not desirable for many Applications Electronic Commerce Software Products Financial Services Corporate Data Healthcare Subscriptions Legal Information

Multiple Security Issues Privacy Integrity Authentication Non-repudiation Interception Spoofing Modification Proof of parties involved

Why do PKIs need Trust ? CAs could issue certificates without checking the owner identity. CAs could deliberately issues false certificates. Private keys could be disclosed by accident, ... or on purpose. False certificates could be inserted into your browser. Portals could contain false URLs. Knowing a principal’s identity does not mean that the principal can be trusted.

Security Algorithms Public Key Algorithms RSA, DSA, Diffie-Hellman, Elliptic Curve Symmetric Algorithms Triple-DES, DES, CAST, RC2, IDEA Hashing Algorithms SHA-1, MD5, RIPEMD

Symmetric Key Encryption If any one’s key is compromised, all keys need to be replaced Not practical or cost effective for Internet environments INTERNET

Public Key Cryptography Public-Key Cryptography is an encryption scheme that uses mathematically related, but not identical keys. Each user has a key pair (public key/private key). Information encrypted with the public key can only be decrypted using the private key. Public Encryption Original Document Encrypted Document Private Decryption Original Document Sender Receiver

What is a Digital Signature ? A Digital Signature is the result of encrypting the Hash of the data to be exchanged. A Hash (or Message Digest) is the process of mathematically reducing a data stream down to a fixed length field. The Hash uniquely represents the original data. The probability of producing the same Hash with two sets of different data is <.001%. Signature Process is opposite to Encryption Process Private Key is used to Sign (encrypt) Data Public Key is used to verify (decrypt) Signature

Digital Signature Process Step 1 . Hash (digest) the data using one of the supported Hashing algorithms, e.g., MD2, MD5, or SHA-1. Step 2 . Encrypt the hashed data using the sender’s private key. Step 3 . Append the signature (and a copy of the sender’s public key) to the end of the data that was signed. Data Hash Encrypt Hash Digital Signature Digital Signature Private Step 1. Step 2. Step 3. Public

Signature Verification Process Step 1 . Hash the original data using the same hashing algorithm. Step 2 . Decrypt the digital signature using the sender’s public key. All digital signatures contain a copy of the signer’s public key. Step 3 . Compare the results of the hashing and the decryption. If the values match then the signature is verified. If the values do not match, then the data or signature was probably modified in transit. Data Hash Decrypt Hash Digital Signature Public Key Step 2. Step 3. Hash Step 1.

The Critical Questions How can the recipient know with certainty the sender’s public key? (to validate a digital signature) How can the sender know with certainty the recipient’s public key? (to send an encrypted message)

Digital Certificates Before B accepts a message with A’s Digital Signature, B wants to be sure that the public key belongs to A and not to someone masquerading as A on an open network One way to be sure, is to use a trusted third party to authenticate that the public key belongs to A. Such a party is known as a Certification Authority (CA) Once A has provided proof of identity, the Certification Authority creates a message containing A’s name and public key. This message is known as a Digital Certificate . Before two parties exchange data using Public Key cryptography, each wants to be sure that the other party is authenticated ~~~~ ~~~~ ~~~~ Digital Signature

Digital Certificates A Digital Certificate is simply an X.509 defined data structure with a Digital Signature. The data represents who owns the certificate, who signed the certificate, and other relevant information CA Authorized When the signature is generated by a Certification Authority (CA), the signature can be viewed as trusted. Since the data is signed, it can not be altered without detection. Extensions can be used to tailor certificates to meet the needs of end applications. Version # Serial # Signature Algorithm Issuer Name Validity Period Subject Name Subject Public Key Issuer Unique ID Subject Unique ID Extensions Digital Signature X.509 Certificate

Certificate Life Cycle Key pair generated Certificate issued Key pair in use Private key compromised Certificate revoked Certificate expires Key pair lifetime exceeded? New key pair generated Re-certify

Certificate Revocation Lists CA periodically publishes a data structure called a certificate revocation list (CRL). Described in X.509 standard. Each revoked certificate is identified in a CRL by its serial number. CRL might be distributed by posting at known Web URL or from CA’s own X.500 directory entry.

PKI Players Registration Authority (RA) to identity proof users Certification Authorities (CA) to issue certificates and CRL’s Repositories (publicly available databases) to hold certificates and CRLs

Certification Authority (CA) Certification Authority Trusted (Third) Party Enrolls and Validates Subscribers Issues and Manages Certificates Manages Revocation and Renewal of Certificates Establishes Policies & Procedures What’s Important Operational Experience High Assurance Security Architecture Scalability Flexibility Interoperability Outsource vs. Inhouse Trustworthiness Certification Authority = Basis of Trust

Registration Authority (RA) Enrolling, de-enrolling, and approving or rejecting requested changes to the certificate attributes of subscribers. Validating certificate applications. Authorizing requests for key-pair or certificate generation and requests for the recovery of backed-up keys. Accepting and authorizing requests for certificate revocation or suspension. Physically distributing personal tokens to and recovering obsolete tokens from people authorized to hold and use them.

Certificate Policy (CP) is … the basis for trust between unrelated entities not a formal “contract” (but implied) a framework that both informs and constrains a PKI implementation a statement of what a certificate means a set of rules for certificate holders a way of giving advice to Relying Parties

Public Key Security Public Key Technology Best Suited to Solve Business Needs Infrastructure = Certification Authorities Services Public Key Technology Digital Certificates Certification Authorities Security Management Technology Infrastructure PRIVACY AUTHENTICATION INTEGRITY NON-REPUDIATION

Authentication/Access Control Can Public Key Technology be used to perform Authentication and Access Control? Sure Can How? Using Digital Signatures and Digital Certificates Digital Signature

SSL Protocol Secure Socket Layer (SSL) is a Network Layer protocol used to secure data on TCP/IP networks. Secure Socket Layer Application and so on ….. HTTP TCP/IP Layer Network Layer FTP NNTP

SSL 2.0 Protocol SSL 2.0 provides encryption between the server and the browser. Browser Connects to Secure Server Cert S {SessKey B } Cert S {Data} SessKey B Browser verifies signature on Cert S Browser generates session key (SessKey B ) Browser encrypts SessKey B using Cert S Server sends copy of Server certificate (Cert S ) to Browser, indicating that SSL 2.0 is enabled Server decrypts SessKey B using it’s private key Browser and Server use SessKey B to encrypt all data exchanged over the Internet

SSL 3.0 with Client Authentication Browser Connects to Secure Server Cert S - SSL 3.0 {SessKey B } Cert S + Cert B {Data} SessKey B Browser verifies signature on Cert S Browser generates session key (SessKey B ) Browser encrypts SessKey B using Cert S Browser asks operator to select a Browser certificate (Cert B ) to access server Server sends copy of Server certificate (Cert S ) to Browser, indicating that SSL 3.0 is enabled with client authentication Server verifies signature on Cert B (Server can check other information as well) Server decrypts SessKey B using it’s private key Browser and Server use SessKey B to encrypt all data exchanged over the Internet

Smart Cards Microprocessor with memory that can generate and store keys and certificates Different form factors and interface mechanisms Cryptographic functions using private key are processed on the card itself

Microprocessor based smart card

Smart Cards and PKI Smart cards are «certificate wallets» Secure storage for: Owner private key Trusted root certificates Smart Cards are a « PC-in-your-Pocket » Generation of owner’s digital signature Smart cards provide: Mobility Security Transparency Issuer branding, loyalty

Digital ID Asymmetric key-pair public key private key X.509 certificate ISO standard public key credentials

Smart card application example: Digital Signature

Smart card in heterogeneous environments Smart cards need readers and drivers Readers desktop or embedded (keyboard, floppy slot) optional display and keypad PC world ready for installation Mac, Unix & Linux ‘waiting’ for USB Drivers PC/SC standard for Windows PC custom developments

Certificate Portability: Smart Cards Holding Certificates Pros Tamper-proof device Portable Visible security/theft indicator Upgradeable Branding, Photos,Mag-stripe Biometric cards, readers coming Cons More expensive than a pure software solution infrastructure Standards issues Multi-application issues

Pay-TV, did you know it’s PKI ? Pay-TV systems installed worldwide 22 millions customers pay-per-view electronic purse Internet Managed and secured with a very high proprietary secured PKI solution based on a smartcard

Signed and Encrypted Email – S/MIME S/MIME – Secure Multipurpose Internet Mail Extensions Prevent email spoofing Helps preventing forged email Helps preventing spam Protect sensitive messages & documents Secure business processes Signed messages S/MIME-based applications

Using PKI Certificates in Outlook (1) Open Outlook . Select Tools from the main menu then choose Options from the drop-down menu. 1

Using PKI Certificates in Outlook (2) Click on the Security tab. 2

Using PKI Certificates in Outlook (3) Click the Settings button. 3

Using PKI Certificates in Outlook (4) In the Security Settings Name field, enter a name for the new Security Setting . Type S/MIME in the Secure Message Format field. Click the Choose button next to the Signing Certificate field. 4

Using PKI Certificates in Outlook (5) Click on the certificate issued by C3 Mail CA . This is your Email Signing certificate. Click OK . 5

Using PKI Certificates in Outlook (6) Choose SHA1 from the Hash Algorithm drop down menu. Click on the Choose button next to the Encryption Certificate field. 6

Using PKI Certificates in Outlook (7) Click on the certificate issued by C3 Mail CA . This is your Email Encryption certificate. Click OK . 7

Using PKI Certificates in Outlook (8) Choose 3DES from the Encryption Certificate drop down box. Check all 3 boxes in the Change Security Settings window. Click OK . 8

Using PKI Certificates in Outlook (9) Click the Apply button then click OK . 9

PKI and Applications

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PKI and Applications