There are a number of standards related to cryptography. Standard algorithms and protocols provide a focus for study; standards for popular applications attract a large amount of cryptanalysis. Encryption standards Data Encryption Standard (DES, now obsolete) Advanced Encryption Standard (AES) RSA the original public key algorithm OpenPGP Hash standards MD5 128-bit (obsolete) SHA-1 160-bit (obsolete) SHA-2 available in 224, 256, 384, and 512-bit variants HMAC keyed hash PBKDF2 Key derivation function (RFC 2898) Digital signature standards Digital Signature Standard (DSS), based on the Digital Signature Algorithm (DSA) RSA Elliptic Curve DSA Public-key infrastructure (PKI) standards X.509 Public Key Certificates Wireless Standards Wired Equivalent Privacy (WEP), severely flawed and superseded by WPA Wi-Fi Protected Access (WPA) better than WEP, a 'pre-standard' partial version of 802.11i 802.11i a.k.a. WPA2, uses AES and other improvements on WEP A5/1 and A5/2 cell phone encryption for GSM U.S. Government Federal Information Processing Standards (FIPS) FIPS PUB 31 Guidelines for Automatic Data Processing Physical Security and Risk Management 1974 FIPS PUB 46-3 Data Encryption Standard (DES) 1999 FIPS PUB 73 Guidelines for Security of Computer Applications 1980 FIPS PUB 74 Guidelines for Implementing and Using the NBS Data Encryption Standard 1981 FIPS PUB 81 DES Modes of Operation 1980 FIPS PUB 102 Guideline for Computer Security Certification and Accreditation 1983 FIPS PUB 112 Password Usage 1985, defines 10 factors to be considered in access control systems that are based on passwords FIPS PUB 113 Computer Data Authentication 1985, specifies a Data Authentication Algorithm (DAA) based on DES, adopted by the Department of Treasury and the banking community to protect electronic fund transfers. FIPS PUB 140-2 Security Requirements for Cryptographic Modules 2001, defines four increasing security levels FIPS PUB 171 Key Management Using ANSI X9.17 (ANSI X9.17-1985) 1992, based on DES FIPS PUB 180-2 Secure Hash Standard (SHS) 2002 defines the SHA family FIPS PUB 181 Automated Password Generator (APG) 1993 FIPS PUB 185 Escrowed Encryption Standard (EES) 1994, a key escrow system that provides for decryption of telecommunications when lawfully authorized. FIPS PUB 186-2 Digital Signature Standard (DSS) 2000 FIPS PUB 190 Guideline for the Use of Advanced Authentication Technology Alternatives 1994 FIPS PUB 191 Guideline for the Analysis of local area network Security 1994 FIPS PUB 196 Entity Authentication Using Public Key Cryptography 1997 FIPS PUB 197 Advanced Encryption Standard (AES) 2001 FIPS PUB 198 The Keyed-Hash Message Authentication Code (HMAC) 2002 Internet Requests for