# PdfEncryptionAlgorithm Enum

Represents an encryption algorithm used in a PDF file.

### Fields

AES | The AES (Advanced Encryption Standard) algorithm (beginning with PDF 1.6). AES is a symmetric block cipher: the same algorithm shall be used for both encryption and decryption, and the length of the data when encrypted is rounded up to a multiple of the block size, which is fixed to always be 16 bytes, as specified in FIPS 197, Strings and streams encrypted with AES shall use a padding scheme that is described in Internet RFC 2898, The Cipher Block Chaining (CBC) mode, which requires an initialization vector, is used. The block size parameter is set to 16 bytes, and the initialization vector is a 16-byte random number that is stored as the first 16 bytes of the encrypted stream or string. |

RC4 | A proprietary encryption algorithm known as RC4. RC4 is a symmetric stream cipher: the same algorithm shall be used for both encryption and decryption, and the algorithm does not change the length of the data. |