sqlite3 用SQLCipher 加密后命令行下如何重新打开和读取

http://sqlcipher.net/sqlcipher-api/#key

PRAGMA key

The process of creating a new, encrypted database is called “keying” the database. SQLCipher uses just-in-time key derivation at the point it is first needed for an operation. This means that the key (and any options) must be set before the first operation on the database. As soon as the database is touched (e.g. SELECT, CREATE TABLE, UPDATE, etc.) and pages need to be read or written, the key is prepared for use.

satckoverflow.com上有人提到过在

sqlite> sqlcipher-shell32.exe test.db

sqlite> PRAGMA KEY = '12345';

给刚打开的数据库设置密码后，马上接着往数据库执行create table和 insert操作。最后用

sqlite> .e

退出该数据库。但是下次再用

sqlite> sqlcipher-shell32.exe test.db

sqlite>.schema

Error: file is encrypted or is not a database

sqlite> PRAGMA KEY = '12345';

Error: file is encrypted or is not a database

遭到提示：Error: file is encrypted or is not a database

根据官方以上英文描述，这个问题就是因为操作上没有遵循just-in-time key derivation的要求，没有首先输密码解密再进行其他操作。

有图为证：

----------------以下为正确操作过程：

SQLite version 3.7.15.2 2013-01-09 11:53:05
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> PRAGMA KEY = '12345';
sqlite> .schema
CREATE TABLE t(name text);
sqlite> select * from t;
n1
sqlite>

----------------以下为错误操作过程：

Enter SQL statements terminated with a ";"
sqlite> .schema
Error: file is encrypted or is not a database
sqlite> PRAGMA KEY = '12345';
sqlite> .schema
Error: file is encrypted or is not a database
sqlite>

确实如此。

以上过程你可以自己亲自验证以下。

注意：通过命令行（ sqlcipher-shell32.exe）执行命令，与通过sqlite3 api调用操作sqlite3数据库，是一样的道理

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