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Determina el método de cifrado del archivo PDF
type
THPDFKeyType = ( k40, k128, aes128, aes256 );
Sintaxis Delphi:
property CryptKeyLength: THPDFKeyType;
Sintaxis C++:
__property THPDFKeyType CryptKeyLength;
Descripción
Utilice CryptKeyLength para elegir la revisión del security handler estándar y el cifrado usado cuando ActivateProtection está habilitado
Valor Significado
k40 Standard security handler V=1, R=2, RC4 with a 40-bit key (PDF 1.1+).
k128 Standard security handler V=2, R=3, RC4 with a 128-bit key (PDF 1.4+).
aes128 Standard security handler V=4, R=4 with crypt filter StdCF (CFM=AESV2). AES-128 in CBC mode with PKCS#7 padding and a 16-byte random initialization vector per ISO 32000-1 7.6.2 / 7.4.4.2 (PDF 1.6+). Since HotPDF v2.4.0 this option encrypts strings and streams with a real AES implementation; earlier builds emitted the AES dictionary but did not actually encrypt content.
aes256 Standard security handler V=5 with crypt filter StdCF (CFM=AESV3). AES-256 in CBC mode with PKCS#7 padding and a 16-byte random initialization vector per Adobe Extension Level 3 / ISO 32000-2 7.6.4 (PDF 1.7+, accepted by Acrobat 9 and later, Foxit, Chrome and the Apple/macOS viewers). Available since HotPDF v2.17.0. The default revision is R=5 with SHA-256 password hashing. Set UseAES256R6 to true to switch to R=6 with the ISO 32000-2 algorithm 2.B "hash dance" (SHA-256 / SHA-384 / SHA-512 + AES-128 mixer); R=6 is required by Acrobat DC and PDF/A-4 validators. Available since HotPDF v2.22.0.
Public-Key Security Handler (PDF 1.7 7.6.5)
Para cifrado basado en certificados (un documento, varios destinatarios), llame a EnablePubKeyEncryption(seed, KeyType, EncryptMetadata) en lugar de establecer UserPassword / OwnerPassword. Los mismos valores de CryptKeyLength se aplican al cifrado simétrico (k40 -> RC4-40 / V=1 + s4 SubFilter, k128 -> RC4-128 / V=2 + s5, aes128 -> AES-128 / V=4 + s5). El llamador debe construir un blob PKCS#7 envelopedData por destinatario (Windows CryptoAPI, OpenSSL o pycryptodome) y agregar cada blob mediante AddPubKeyRecipient; la clave de cifrado del archivo se deriva mediante el algoritmo 9 (SHA-1 de la semilla concatenada con los binarios envelope). Disponible desde HotPDF v2.33.0
Ejemplo de código
HPDF.OwnerPassword := 'password'; // Set owner password (required to change security settings)
HPDF.UserPassword := 'user'; // Set user password (required to open the document)
HPDF.ProtectOptions := [poEdit, poAnnot]; // Disallow editing and annotations
HPDF.ActivateProtection := true; // Enable PDF security
Véase también: ActivateProtection, OwnerPassword, ProtectOptions, UserPassword
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