Transforms the next record of plaintext according to the
algorithm you specify in the ENCRYPT$INIT call. This routine
performs either an encryption or decryption operation.
Format
ENCRYPT$ENCRYPT context, input, output [,output-length] [,p1]
1 – Arguments
context
type: longword integer (signed)
access: write only
mechanism: by reference
Context area initialized when ENCRYPT$INIT completes execution.
The context argument is the address of a longword of unspecified
interpretation that is used to convey context between encryption
operations.
input
type: char_string
access: read only
mechanism: by descriptor
Plaintext record to encrypt. The input argument is the address
of a descriptor pointing to a byte-aligned buffer containing the
input record to the encryption operation.
output
type: char_string
access: write only by descriptor
mechanism:
Ciphertext record that results when ENCRYPT$ENCRYPT completes
execution. The output argument is the address of a descriptor
pointing to a byte-aligned buffer that will contain the output
record from the encryption operation.
If the descriptor is dynamic and insufficient space is allocated
to contain the output record, storage is allocated from dynamic
memory.
ENCRYPT$ENCRYPT adjusts the length of the output descriptor,
if possible, to reflect the actual length of the output string.
If the descriptor type is not DSC$K_DTYPE_VS (varying string),
DSC$K_DTYPE_V (varying), or DSC$K_DTYPE_D (dynamic), the routine
takes the actual output count from the output-length argument.
The output buffer must be able to accommodate a padded block to
an increment of the block length. For AES this is 16 bytes and
for DES, 8 bytes.
output-length
type: word integer
access: write only
mechanism: by reference
Optional argument. Number of bytes that ENCRYPT$ENCRYPT wrote to
the output buffer. The output-length argument is the address of a
word containing the number of bytes written to the output buffer.
Some encryption algorithms have specific requirements for the
length of the input and output strings. In particular, DESECB
and DESCBC pad input data with from 1 to 7 bytes to form complete
64-bit blocks for operation. The values of the pad characters are
indeterminate.
When you decrypt fewer than 8 bytes, preserve and present to
ENCRYPT$DECRYPT the full 8 bytes resulting from ENCRYPT$ENCRYPT.
Retain the byte count of the input data in order to strip
trailing pad bytes after a subsequent decryption operation.
Note that the AES block mode algorithms (AESCBCxxx and AESECBxxx)
pad the data to even 16 byte block boundaries. For AES, one byte
encrypts and decrypts to 16 bytes, 72 bytes to 80, and so forth.
The AES padding character is a HEX number of bytes indicating the
number of bytes padded. For example, the one-byte encrypted pad
would decrypt to 15 characters of 0F following the one encrypted
byte of data. For the 72 bytes of data, eight bytes of padding
characters (08 08 ... 08), would follow the 72 bytes of encrypted
data. DESECB and DESCBC modes always pad with characters of
zeros. The character stream modes (AESCFBxxx, AESOFBxxx, DESCFB).
In order that the output-length will match the actual number of
data bytes, do not pad the data.
p1
type: quadword[1] (DES), quadword[2] (AES)
access: read only
mechanism: by reference
Optional argument. The p1 argument is the address of a quadword
initialization vector used to seed the three modes (DESECB,
DESCFB, and DESMAC) of the DES algorithm for which it is
applicable. The DES IV initialization vector is a quadword
reference, to an eight byte value.
For AES, the optional P1 argument for the AES IV initialization
vector is a reference to a 16 byte (two quadwords) value.
If you omit this argument, the initialization vector used is
the residue of the previous use of the specified context block.
ENCRYPT$INIT initializes the context block with an initialization
vector of zero.