39 DBMS_CRYPTO

Overview

DBMS_CRYPTO contains basic cryptographic functions and procedures. To use this package correctly and securely, a general level of security expertise is assumed.

The DBMS_CRYPTO package enables encryption and decryption for common Oracle datatypes, including RAW and large objects (LOBs), such as images and sound. Specifically, it supports BLOBs and CLOBs. In addition, it provides Globalization Support for encrypting data across different database character sets.

The following cryptographic algorithms are supported:

• Data Encryption Standard (DES), Triple DES (3DES, 2-key and 3-key)

• Advanced Encryption Standard (AES)

• MD5, MD4, and SHA-1 cryptographic hashes

• MD5 and SHA-1 Message Authentication Code (MAC)

Block cipher modifiers are also provided with DBMS_CRYPTO. You can choose from several padding options, including PKCS (Public Key Cryptographic Standard) #5, and from four block cipher chaining modes, including Cipher Block Chaining (CBC).

Table 39-1 lists the DBMS_CRYPTO package features in comparison to the other PL/SQL encryption package, the DBMS_OBFUSCATION_TOOLKIT.

DBMS_CRYPTO is intended to replace the DBMS_OBFUSCATION_TOOLKIT, providing greater ease of use and support for a range of algorithms to accommodate new and existing systems. Specifically, 3DES_2KEY and MD4 are provided for backward compatibility. It is not recommended that you use these algorithms because they do not provide the same level of security as provided by 3DES, AES, MD5, or SHA-1.

Security Model

Oracle Database installs this package in the SYS schema. You can then grant package access to existing users and roles as needed.

Types

Parameters for the DBMS_CRYPTO subprograms use these datatypes:

Algorithms

The following cryptographic algorithms, modifiers, and cipher suites are predefined in this package.

^Footnote 1 Complies with IETF RFC 2104 standard

^Footnote 1 See Table 39-5, "DBMS_CRYPTO Encryption Algorithms"

^Footnote 2 See Table 39-7, "DBMS_CRYPTO Block Cipher Chaining Modifiers"

^Footnote 3 See Table 39-8, "DBMS_CRYPTO Block Cipher Padding Modifiers"

Restrictions

The VARCHAR2 datatype is not directly supported by DBMS_CRYPTO. Before you can perform cryptographic operations on data of the type VARCHAR2, you must convert it to the uniform database character set AL32UTF8, and then convert it to the RAW datatype. After performing these conversions, you can then encrypt it with the DBMS_CRYPTO package.

Exceptions

Table 39-9 lists exceptions that have been defined for DBMS_CRYPTO.

Operational Notes

• When to Use Encrypt and Decrypt Procedures or Functions

• When to Use Hash or Message Authentication Code (MAC) Functions

• About Generating and Storing Encryption Keys

• Conversion Rules

Examples

The following listing shows PL/SQL block encrypting and decrypting pre-defined 'input_string' using 256-bit AES algorithm with Cipher Block Chaining and PKCS#5 compliant padding.

DECLARE
   input_string       VARCHAR2 (200) :=  'Secret Message';
   output_string      VARCHAR2 (200);
   encrypted_raw      RAW (2000);             -- stores encrypted binary text
   decrypted_raw      RAW (2000);             -- stores decrypted binary text
   num_key_bytes      NUMBER := 256/8;        -- key length 256 bits (32 bytes)
   key_bytes_raw      RAW (32);               -- stores 256-bit encryption key
   encryption_type    PLS_INTEGER :=          -- total encryption type
                            DBMS_CRYPTO.ENCRYPT_AES256
                          + DBMS_CRYPTO.CHAIN_CBC
                          + DBMS_CRYPTO.PAD_PKCS5;
BEGIN
   DBMS_OUTPUT.PUT_LINE ( 'Original string: ' || input_string);
   key_bytes_raw := DBMS_CRYPTO.RANDOMBYTES (num_key_bytes);
   encrypted_raw := DBMS_CRYPTO.ENCRYPT
      (
         src => UTL_I18N.STRING_TO_RAW (input_string,  'AL32UTF8'),
         typ => encryption_type,
         key => key_bytes_raw
      );
    -- The encrypted value "encrypted_raw" can be used here
 
   decrypted_raw := DBMS_CRYPTO.DECRYPT
      (
         src => encrypted_raw,
         typ => encryption_type,
         key => key_bytes_raw
      );
   output_string := UTL_I18N.RAW_TO_CHAR (decrypted_raw, 'AL32UTF8');
 
   DBMS_OUTPUT.PUT_LINE ('Decrypted string: ' || output_string);
END;

DECRYPT Function

This function decrypts RAW data using a stream or block cipher with a user supplied key and optional IV (initialization vector).

DBMS_CRYPTO.DECRYPT(
   src IN RAW,
   typ IN PLS_INTEGER,
   key IN RAW,
   iv  IN RAW DEFAULT NULL)
 RETURN RAW;

pragma restrict_references(decrypt,WNDS,RNDS,WNPS,RNPS);

DECRYPT Procedures

These procedures decrypt LOB data using a stream or block cipher with a user supplied key and optional IV (initialization vector).

DBMS_CRYPTO.DECRYPT(
   dst IN OUT NOCOPY BLOB,
   src IN            BLOB,
   typ IN            PLS_INTEGER,
   key IN            RAW,
   iv  IN            RAW          DEFAULT NULL);

DBMS_CRYPT.DECRYPT(
   dst IN OUT NOCOPY CLOB         CHARACTER SET ANY_CS,
   src IN            BLOB,
   typ IN            PLS_INTEGER,
   key IN            RAW,
   iv  IN            RAW          DEFAULT NULL);

pragma restrict_references(decrypt,WNDS,RNDS,WNPS,RNPS);

ENCRYPT Function

This function encrypts RAW data using a stream or block cipher with a user supplied key and optional IV (initialization vector).

DBMS_CRYPTO.ENCRYPT(
   src IN RAW,
   typ IN PLS_INTEGER,
   key IN RAW,
   iv  IN RAW          DEFAULT NULL)
 RETURN RAW;

pragma restrict_references(encrypt,WNDS,RNDS,WNPS,RNPS);

ENCRYPT Procedures

These procedures encrypt LOB data using a stream or block cipher with a user supplied key and optional IV (initialization vector).

DBMS_CRYPTO.ENCRYPT(
   dst IN OUT NOCOPY BLOB,
   src IN            BLOB,
   typ IN            PLS_INTEGER,
   key IN            RAW,
   iv  IN            RAW          DEFAULT NULL);

DBMS_CRYPTO.ENCRYPT(
   dst IN OUT NOCOPY BLOB,
   src IN            CLOB         CHARACTER SET ANY_CS,
   typ IN            PLS_INTEGER,
   key IN            RAW,
   iv  IN            RAW          DEFAULT NULL);

pragma restrict_references(encrypt,WNDS,RNDS,WNPS,RNPS);

HASH Function

A one-way hash function takes a variable-length input string, the data, and converts it to a fixed-length (generally smaller) output string called a hash value. The hash value serves as a unique identifier (like a fingerprint) of the input data. You can use the hash value to verify whether data has been changed or not.

Note that a one-way hash function is a hash function that works in one direction. It is easy to compute a hash value from the input data, but it is hard to generate data that hashes to a particular value. Consequently, one-way hash functions work well to ensure data integrity. Refer to "When to Use Hash or Message Authentication Code (MAC) Functions" for more information about using one-way hash functions.

This function applies to data one of the supported cryptographic hash algorithms listed in Table 39-3.

DBMS_CRYPTO.Hash (
   src IN RAW,
   typ IN PLS_INTEGER)
 RETURN RAW;

DBMS_CRYPTO.Hash (
   src IN BLOB,
   typ IN PLS_INTEGER)
 RETURN RAW;

DBMS_CRYPTO.Hash (
   src IN CLOB CHARACTER SET ANY_CS,
   typ IN PLS_INTEGER)
 RETURN RAW;

pragma restrict_references(hash,WNDS,RNDS,WNPS,RNPS);

MAC Function

A Message Authentication Code, or MAC, is a key-dependent one-way hash function. MACs have the same properties as the one-way hash function described in "HASH Function", but they also include a key. Only someone with the identical key can verify the hash. Also refer to "When to Use Hash or Message Authentication Code (MAC) Functions" for more information about using MACs.

This function applies MAC algorithms to data to provide keyed message protection. See Table 39-4 for a list of MAC algorithms that have been defined for this package.

DBMS_CRYPTO.MAC (
   src IN RAW,
   typ IN PLS_INTEGER,
   key IN RAW)
 RETURN RAW;

DBMS_CRYPTO.MAC (
   src IN BLOB,
   typ IN PLS_INTEGER
   key IN RAW)
 RETURN RAW;

DBMS_CRYPTO.MAC (
   src IN CLOB CHARACTER SET ANY_CS,
   typ IN PLS_INTEGER
   key IN RAW)
 RETURN RAW;

pragma restrict_references(mac,WNDS,RNDS,WNPS,RNPS);

RANDOMBYTES Function

This function returns a RAW value containing a cryptographically secure pseudo-random sequence of bytes, which can be used to generate random material for encryption keys. The RANDOMBYTES function is based on the RSA X9.31 PRNG (Pseudo-Random Number Generator).

DBMS_CRYPTO.RANDOMBYTES (
   number_bytes IN POSITIVE)
 RETURN RAW;

pragma restrict_references(randombytes,WNDS,RNDS,WNPS,RNPS);

RANDOMINTEGER Function

This function returns an integer in the complete range available for the Oracle BINARY_INTEGER datatype.

DBMS_CRYPTO.RANDOMINTEGER
 RETURN BINARY_INTEGER;

pragma restrict_references(randominteger,WNDS,RNDS,WNPS,RNPS);

RANDOMNUMBER Function

This function returns an integer in the Oracle NUMBER datatype in the range of [0..2**128-1].

DBMS_CRYPTO.RANDOMNUMBER
 RETURN NUMBER;

pragma restrict_references(randomnumber,WNDS,RNDS,WNPS,RNPS);