robertamarton commented on a change in pull request #1825: [TRAFODION-3293] Add
the AES_ENCRYPT Function in the Trafodion SQL Reference Manual
URL: https://github.com/apache/trafodion/pull/1825#discussion_r273144283
##########
File path:
docs/sql_reference/src/asciidoc/_chapters/sql_functions_and_expressions.adoc
##########
@@ -487,6 +487,141 @@ LARGEINT if the precision of the argument is greater
than or equal to
ABS (-20 + 12)
```
+<<<
+[[aes_encrypt_function]]
+== AES_ENCRYPT Function
+
+The AES_ENCRYPT function encrypts a `_string_` using a specified encryption
`_key_` with the AES (Advanced Encryption Standard) algorithm and returns a
binary string.
+
+This function prevents sensitive data from being visible to the public. For
example, use the AES_ENCRYPT function to encrypt person identity number to
preserve user confidentiality.
+
+`AES_ENCRYPT (_string_, _key_)`
+
+[[syntax_description_of_aes_encrypt]]
+=== Syntax Description of AES_ENCRYPT
+
+* `_string_`
++
+is the data to be encrypted.
+
+* `_key_`
++
+is the encryption key to encrypt the `_string_`.
+
++
+TIP: The CQD `block_encryption_mode` controls the mode for the block-based
encryption algorithm. The default mode is the aes-128-ecb, which means the
encryption using a key length of 128 bits and the ECB mode.
+
++
+[cols="50%,50%"]
+|===
+^| *Value* ^| *Mode*
+^| 0 ^| aes-128-ecb
+^| 1 ^| aes-192-ecb
+^| 2 ^| aes-256-ecb
+|===
+
++
+*Example*
+
++
+The following examples show that the AES_ENCRYPT function returns the
different results based on the different modes.
+
++
+** The mode aes_192_ecb is in effect.
+
++
+```
+CQD BLOCK_ENCRYPTION_MODE '1';
+
+--- SQL operation complete.
+```
+
++
+```
+SELECT AES_ENCRYPT ('Technical_Writer','Coder') FROM DUAL;
+
+(EXPR)
+--------------------------------
+4}\îî¢Øã^ûh<á¼Æ7õé³ê!cH^Ð
+```
+
++
+** The mode aes_256_ecb is in effect.
+
++
+```
+CQD BLOCK_ENCRYPTION_MODE '2';
+
+--- SQL operation complete.
+```
+
++
+```
+SELECT AES_ENCRYPT ('Technical_Writer','Coder') FROM DUAL;
+
+(EXPR)
+--------------------------------
+Ô_8ÆðÑ=Uú2g1¥@°Ô3yä
+
+--- 1 row(s) selected.
+```
+
+[[considerations_for_aes_encrypt]]
+=== Considerations for AES_ENCRYPT
+
+Either argument cannot be NULL.
Review comment:
It looks like openssl defines the max key length to use. Its size depends
on the version of openSSL installed. On development systems it is 64
(/usr/bin/openssl/evp.h) but it looks like it can go up to 512 and beyond
(https://github.com/openssl/openssl/issues/4777).
I looked up openssl (man EVP_EncryptUpdate):
EVP_EncryptUpdate() encrypts inl bytes from the buffer in and writes the
encrypted version to out. This function can be called multiple times to encrypt
successive blocks of data. The amount of data written depends on the block
alignment of the encrypted data: as a result the amount of data written may be
anything from zero bytes to (inl + cipher_block_size - 1) so out should contain
sufficient room. The actual number of bytes written is placed in outl.
So, I guess for now, not mention the encrypted length until we can come up
with a formula.
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