1## SQLCipher 2 3SQLCipher extends the [SQLite](https://www.sqlite.org) database library to add security enhancements that make it more suitable for encrypted local data storage such as on-the-fly encryption, tamper evidence, and key derivation. Based on SQLite, SQLCipher closely tracks SQLite and periodically integrates stable SQLite release features. 4 5SQLCipher is maintained by Zetetic, LLC, the official site can be found [here](https://www.zetetic.net/sqlcipher/). 6 7## Features 8 9- Fast performance with as little as 5-15% overhead for encryption on many operations 10- 100% of data in the database file is encrypted 11- Good security practices (CBC mode, HMAC, key derivation) 12- Zero-configuration and application level cryptography 13- Algorithms provided by the peer reviewed OpenSSL crypto library. 14- Configurable crypto providers 15 16## Contributions 17 18We welcome contributions, to contribute to SQLCipher, a [contributor agreement](https://www.zetetic.net/contributions/) needs to be submitted. All submissions should be based on the `prerelease` branch. 19 20## Compiling 21 22Building SQLCipher is almost the same as compiling a regular version of 23SQLite with two small exceptions: 24 25 1. You *must* define `SQLITE_HAS_CODEC` and `SQLITE_TEMP_STORE=2` when building sqlcipher. 26 2. If compiling against the default OpenSSL crypto provider, you will need to link libcrypto 27 28Example Static linking (replace /opt/local/lib with the path to libcrypto.a). Note in this 29example, `--enable-tempstore=yes` is setting `SQLITE_TEMP_STORE=2` for the build. 30 31 $ ./configure --enable-tempstore=yes CFLAGS="-DSQLITE_HAS_CODEC" \ 32 LDFLAGS="/opt/local/lib/libcrypto.a" 33 $ make 34 35Example Dynamic linking 36 37 $ ./configure --enable-tempstore=yes CFLAGS="-DSQLITE_HAS_CODEC" \ 38 LDFLAGS="-lcrypto" 39 $ make 40 41## Encrypting a database 42 43To specify an encryption passphrase for the database via the SQL interface you 44use a pragma. The passphrase you enter is passed through PBKDF2 key derivation to 45obtain the encryption key for the database 46 47 PRAGMA key = 'passphrase'; 48 49Alternately, you can specify an exact byte sequence using a blob literal. If you 50use this method it is your responsibility to ensure that the data you provide is a 5164 character hex string, which will be converted directly to 32 bytes (256 bits) of 52key data without key derivation. 53 54 PRAGMA key = "x'2DD29CA851E7B56E4697B0E1F08507293D761A05CE4D1B628663F411A8086D99'"; 55 56To encrypt a database programatically you can use the `sqlite3_key` function. 57The data provided in `pKey` is converted to an encryption key according to the 58same rules as `PRAGMA key`. 59 60 int sqlite3_key(sqlite3 *db, const void *pKey, int nKey); 61 62`PRAGMA key` or `sqlite3_key` should be called as the first operation when a database is open. 63 64## Changing a database key 65 66To change the encryption passphrase for an existing database you may use the rekey pragma 67after you've supplied the correct database password; 68 69 PRAGMA key = 'passphrase'; -- start with the existing database passphrase 70 PRAGMA rekey = 'new-passphrase'; -- rekey will reencrypt with the new passphrase 71 72The hex rekey pragma may be used to rekey to a specific binary value 73 74 PRAGMA rekey = "x'2DD29CA851E7B56E4697B0E1F08507293D761A05CE4D1B628663F411A8086D99'"; 75 76This can be accomplished programtically by using sqlite3_rekey; 77 78 sqlite3_rekey(sqlite3 *db, const void *pKey, int nKey) 79 80## Support 81 82The primary avenue for support and discussions is the SQLCipher discuss site: 83 84https://discuss.zetetic.net/c/sqlcipher 85 86Issues or support questions on using SQLCipher should be entered into the 87GitHub Issue tracker: 88 89https://github.com/sqlcipher/sqlcipher/issues 90 91Please DO NOT post issues, support questions, or other problems to blog 92posts about SQLCipher as we do not monitor them frequently. 93 94If you are using SQLCipher in your own software please let us know at 95support@zetetic.net! 96 97## License 98 99Copyright (c) 2016, ZETETIC LLC 100All rights reserved. 101 102Redistribution and use in source and binary forms, with or without 103modification, are permitted provided that the following conditions are met: 104 * Redistributions of source code must retain the above copyright 105 notice, this list of conditions and the following disclaimer. 106 * Redistributions in binary form must reproduce the above copyright 107 notice, this list of conditions and the following disclaimer in the 108 documentation and/or other materials provided with the distribution. 109 * Neither the name of the ZETETIC LLC nor the 110 names of its contributors may be used to endorse or promote products 111 derived from this software without specific prior written permission. 112 113THIS SOFTWARE IS PROVIDED BY ZETETIC LLC ''AS IS'' AND ANY 114EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 115WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 116DISCLAIMED. IN NO EVENT SHALL ZETETIC LLC BE LIABLE FOR ANY 117DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 118(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 119LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 120ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 121(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 122SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 123