HASH scalar function

The HASH function returns a 128-bit, 160-bit, 256-bit or 512-bit hash of the input data, depending on the algorithm selected, and is intended for cryptographic purposes.

The schema is SYSIBM.

string-expression: An expression that represents the string value to be hashed. This expression must return a built-in character string, graphic string, binary string, numeric value, Boolean value, or datetime value. If the value is not a character, graphic, or binary string, it is implicitly cast to VARCHAR before the function is evaluated.
algorithm: An expression that returns a value that indicates which algorithm is to be used for hashing. The expression must return a value that has a built-in numeric, a CHAR, or a VARCHAR data type. In a Unicode database, the expression can also return a GRAPHIC or VARGRAPHIC data type. If the value is not an INTEGER, it is cast to INTEGER before the function is evaluated. If no algorithm is specified, the default algorithm value of 0 is used.

Table 1 shows the algorithm used, the result size, and the number of return values for each algorithm value.

Table 1. Resulting size from each algorithm
Algorithm value	Algorithm	Result size	Number of return values
0	MD5	128 bit	2¹²⁸
1	SHA1	160 bit	2¹⁶⁰
2	SHA2_256	256 bit	2²⁵⁶
3	SHA2_512	512 bit	2⁵¹²

Note that security flaws have been identified in both the SHA1 and MD5 algorithms. You can find acceptable hash algorithms in applicable compliance documentation, such as National Institute of Standards and Technology (NIST) Special Publication 800-131A.

Result

The data type of the result is VARBINARY. If any argument can be null, the result can be null. If any argument is null, the result is the null value.

Example

values  hash('Charlie at IBM', 1)
result is x'D6E42303462491FC696EAC53C1B086A5034735A7'