PgpCore

A .NET Core class library for using PGP.

This is based on ChoPGP but updated to .NET Standard and to add in a missing utilities class.

Installation

To use PgpCore in your C# project download it from NuGet.

Once you have the PgpCore libraries properly referenced in your project, you can include calls to them in your code.

Add the following namespaces to use the library:

using PgpCore;

Dependencies

BouncyCastle.Cryptography (>= 2.4.0)

Usage

PgpCore targets both .NET Standard 2.0 (for broad compatibility with .NET Framework and older .NET Core) and .NET 10.

Upgrading to v8.0

Version 8.0 hardens the cryptographic defaults and removes long-deprecated members. These are breaking changes — review the following before upgrading:

Changed defaults (only affects code that relied on the old defaults without setting them explicitly):

Setting	Old default	New default
`SymmetricKeyAlgorithm`	`TripleDes`	`Aes256`
`HashAlgorithmTag`	`Sha1`	`Sha256`
`CompressionAlgorithm`	`Uncompressed`	`Zip`
`GenerateKey` `strength`	`1024`	`3072`
`GenerateKey` `certainty`	`8`	`24`

To reproduce the old behaviour, set the properties explicitly, e.g. new PGP(keys) { SymmetricKeyAlgorithm = SymmetricKeyAlgorithmTag.TripleDes, HashAlgorithmTag = HashAlgorithmTag.Sha1, CompressionAlgorithm = CompressionAlgorithmTag.Uncompressed }. Data produced with the new defaults remains readable by any modern OpenPGP implementation (including GnuPG).

Removed members:

IEncryptionKeys.PublicKey / EncryptionKeys.PublicKey → use MasterKey or EncryptKeys.FirstOrDefault().
IEncryptionKeys.PublicKeys / EncryptionKeys.PublicKeys → use EncryptKeys.
VerifyClear(string input, string output) → use VerifyAndReadClearArmoredString(string input) (the removed overload could never return its output).
PGP.Instance static singleton → construct a PGP instance directly (the mutable singleton with settable algorithm properties was not thread-safe).

Exceptions: operations now throw specific exception types deriving from PgpCoreException (e.g. IncorrectPassphraseException, NoDecryptionKeyException, NotEncryptedDataException, MessageIntegrityException) instead of generic ArgumentException / BouncyCastle PgpException. PgpCoreException now derives from System.Exception (in v7.x it derived from BouncyCastle's PgpException); update any catch (PgpException) blocks that relied on the old hierarchy.

Generated key structure: GenerateKey now produces a certify/sign master key plus a separate encryption subkey, matching what GnuPG and other mainstream implementations emit. Previously a single master key carried every capability, which meant the signature-only algorithms (EdDsa, ECDsa, Dsa) produced a key that could not encrypt at all (#285). See PublicKeyAlgorithm for the algorithm pairings. Two consequences worth noting:

Messages are now encrypted to the subkey's key id, so GetRecipients returns the subkey id rather than the master key id for keys generated by v8.1 and later.
Keys generated by earlier versions continue to work unchanged for both encryption and decryption; only newly generated keys have the new structure.

Behaviour changes since v8.0.0:

Expired and revoked keys are no longer selected for encryption automatically. Previously an expired public key was encrypted to without any warning (#71); now NoEncryptionKeyException is thrown when the only candidates are expired or revoked, matching gpg's behaviour. Among valid keys, the newest is preferred, so a newly issued subkey takes over from the one it replaces (#210). To encrypt to an expired key deliberately, select it explicitly with UseEncryptionKey.
Verify throws for encrypted input regardless of throwIfEncrypted. Previously, with the parameter at its default of false, Verify returned true when the message was merely encrypted to a known key id — a result any sender can produce, unrelated to any signature. Use DecryptAndVerify for encrypted-and-signed messages.
Keys generated without a passphrase are stored unencrypted, as gpg stores them. Previously the secret key material was encrypted with the empty string, which made gpg and Kleopatra demand a non-empty passphrase before the key could be used (#308).

Azure Function Example

If you want a (basic) example of how you can use an Azure Function to encrypt/decrypt from Azure Blob Storage I've created a sample project here.

Performance

By default encrypted files are armoured. It is suggested that for larger files this is disabled as it can significantly increase the file size and processing time. To disable armouring set the armour property to false.

Settings

Compression Algorithm
Symmetric Key Algorithm
Pgp Signature Type
Public Key Algorithm
File Type
Hash Algorithm Tag
Ignore Integrity Check Failure
Text Encoding

Exceptions

See Exceptions for the exception types thrown by operations.

Generate Key

Generate a new public and private key for the provided username and password.

gpg --gen-key

GenerateKey

using (PGP pgp = new PGP())
{
	// Generate keys
	pgp.GenerateKey(new FileInfo(@"C:\TEMP\Keys\public.asc"), new FileInfo(@"C:\TEMP\Keys\private.asc"), "email@email.com", "password");
}

Inspect

Inspect the provided file, stream or string and return a PGPInspectResult object that contains details on the messages encryption and sign status as well as additional information on filename, headers, etc. where available.

gpg --list-packets "C:\TEMP\Content\encrypted.pgp"

Inspect File

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
FileInfo privateKey = new FileInfo(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey, privateKey, "password");

// Reference input file
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\encrypted.pgp");

// Inspect
PGP pgp = new PGP();
PgpInspectResult result = await pgp.InspectAsync(inputFile);

Inspect Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
using (Stream privateKeyStream = new FileStream(@"C:\TEMP\Keys\private.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(publicKeyStream, privateKeyStream, "password");

PGP pgp = new PGP(encryptionKeys);

// Reference input stream
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\encrypted.pgp", FileMode.Open))
	// Inspect
	PgpInspectResult result = await pgp.InspectAsync(inputFileStream);

Inspect String

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
string privatyeKey = File.ReadAllText(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey, privateKey, "password");

// Inspect
PGP pgp = new PGP(encryptionKeys);
PgpInspectResult result = await pgp.InspectAsync("String to inspect");

Encrypt

Encrypt the provided file, stream or string using a public key.

Optional headers can be provided to include in the encrypted file. These can be set by providing a Dictionary<string, string> to the headers parameter. The key of the dictionary will be the header name and the value will be the header value.

gpg --output "C:\TEMP\Content\encrypted.pgp" --encrypt "C:\TEMP\Content\content.txt"

Encrypt File

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

// Reference input/output files
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\content.txt");
FileInfo encryptedFile = new FileInfo(@"C:\TEMP\Content\encrypted.pgp");

// Encrypt
PGP pgp = new PGP(encryptionKeys);
await pgp.EncryptAsync(inputFile, encryptedFile);

Encrypt Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(publicKeyStream);

PGP pgp = new PGP(encryptionKeys);

// Reference input/output files
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\content.txt", FileMode.Open))
using (Stream outputFileStream = File.Create(@"C:\TEMP\Content\encrypted.pgp"))
	// Encrypt
	await pgp.EncryptAsync(inputFileStream, outputFileStream);

Encrypt String

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

// Encrypt
PGP pgp = new PGP(encryptionKeys);
string encryptedContent = await pgp.EncryptAsync("String to encrypt");

Sign

Sign the provided file or stream using a private key.

Optional headers can be provided to include in the signed file. These can be set by providing a Dictionary<string, string> to the headers parameter. The key of the dictionary will be the header name and the value will be the header value.

gpg --output "C:\TEMP\Content\content.txt" --sign "C:\TEMP\Content\signed.pgp"

Sign File

// Load keys
FileInfo privateKey = new FileInfo(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(privateKey, "password");

// Reference input/output files
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\content.txt");
FileInfo signedFile = new FileInfo(@"C:\TEMP\Content\signed.pgp");

// Sign
PGP pgp = new PGP(encryptionKeys);
await pgp.SignAsync(inputFile, signedFile);

Sign Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream privateKeyStream = new FileStream(@"C:\TEMP\Keys\private.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(privateKeyStream, "password");

PGP pgp = new PGP(encryptionKeys);

// Reference input/output files
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\content.txt", FileMode.Open))
using (Stream outputFileStream = File.Create(@"C:\TEMP\Content\signed.pgp"))
	// Sign
	await pgp.SignAsync(inputFileStream, outputFileStream);

Sign String

// Load keys
string privateKey = File.ReadAllText(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(privateKey, "password");

PGP pgp = new PGP(encryptionKeys);

// Sign
string signedContent = await pgp.SignAsync("String to sign");

Clear Sign

Clear sign the provided file, stream, or string using a private key so that it is still human readable. A common use of digital signatures is to sign usenet postings or email messages. In such situations it is undesirable to compress the document while signing it. This is because the signature would then depend on the compression algorithm used. This is problematic when different people use different compression algorithms. To overcome this problem, the OpenPGP digital signature format has a special type of signature that is not computed on the message itself. Instead, the signature is computed on a "cleartext" version of the message - a version that is exactly the same as the original message except that it is not compressed and certain types of information (such as the end of line markers) are not included. This cleartext version is then compressed and the signature is appended to the compressed cleartext to produce the final message.

gpg --output "C:\TEMP\Content\content.txt" --clearsign "C:\TEMP\Content\clearSigned.pgp"

Clear Sign File

// Load keys
FileInfo privateKey = new FileInfo(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(privateKey, "password");

// Reference input/output files
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\content.txt");
FileInfo signedFile = new FileInfo(@"C:\TEMP\Content\signed.pgp");

// Sign
PGP pgp = new PGP(encryptionKeys);
await pgp.ClearSignAsync(inputFile, signedFile);

Clear Sign Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream privateKeyStream = new FileStream(@"C:\TEMP\Keys\private.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(privateKeyStream, "password");

PGP pgp = new PGP(encryptionKeys);

// Reference input/output files
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\content.txt", FileMode.Open))
using (Stream outputFileStream = File.Create(@"C:\TEMP\Content\signed.pgp"))
	// Sign
	await pgp.ClearSignAsync(inputFileStream, outputFileStream);

Clear Sign String

// Load keys
string privateKey = File.ReadAllText(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(privateKey, "password");

PGP pgp = new PGP(encryptionKeys);

// Sign
string signedContent = await pgp.ClearSignAsync("String to sign");

Detached Sign

Produce a signature for the provided file, stream or string as a separate file, leaving the original content untouched, or verify a detached signature against the original content. Verification is cryptographic: the signature must have been made over exactly the supplied content by one of the supplied verification keys.

gpg --detach-sign "C:\TEMP\Content\content.txt"

Detached Sign File

// Load keys
FileInfo privateKey = new FileInfo(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(privateKey, "password");

// Reference input/output files
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\content.txt");
FileInfo signatureFile = new FileInfo(@"C:\TEMP\Content\content.txt.sig");

// Sign
PGP pgp = new PGP(encryptionKeys);
await pgp.SignDetachedAsync(inputFile, signatureFile);

Verify Detached Signature

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

// Reference the original content and the signature
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\content.txt");
FileInfo signatureFile = new FileInfo(@"C:\TEMP\Content\content.txt.sig");

// Verify
PGP pgp = new PGP(encryptionKeys);
bool verified = await pgp.VerifyDetachedAsync(inputFile, signatureFile);

Encrypt and Sign

Encrypt the provided file, stream or string using a public key and sign using your private key. You usually encrypt with the public key of your counterparty so they can decrypt with their private key and sign with your private key so they can verify with your public key.

Although this method is called EncryptAndSign the signature will actually be included within the encrypted message rather than being appended to the encrypted message. This ensures that the original message was composed by the holder of the private key.

gpg --encrypt --sign --recipient 'some user ID value' "C:\TEMP\keys\content.txt"

Encrypt File And Sign

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
FileInfo privateKey = new FileInfo(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey, privateKey, "password");

// Reference input/output files
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\content.txt");
FileInfo encryptedSignedFile = new FileInfo(@"C:\TEMP\Content\encryptedSigned.pgp");

// Encrypt and Sign
PGP pgp = new PGP(encryptionKeys);
await pgp.EncryptAndSignAsync(inputFile, encryptedSignedFile);

Encrypt Stream And Sign

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
using (Stream privateKeyStream = new FileStream(@"C:\TEMP\Keys\private.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(publicKeyStream, privateKeyStream, "password");

PGP pgp = new PGP(encryptionKeys);

// Reference input/output files
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\content.txt", FileMode.Open))
using (Stream outputFileStream = File.Create(@"C:\TEMP\Content\signed.pgp"))
	// Encrypt and Sign
	await pgp.EncryptAndSignAsync(inputFileStream, outputFileStream);

Encrypt String And Sign

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
string privateKey = File.ReadAllText(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey, privateKey, "password");

PGP pgp = new PGP(encryptionKeys);

// Encrypt and Sign
string encryptedSignedContent = await pgp.EncryptAndSignAsync("String to encrypt and sign");

Decrypt

Decrypt the provided file, stream or string using the matching private key and passphrase.

gpg --output "C:\TEMP\Content\decrypted.txt" --decrypt "C:\TEMP\Content\encrypted.pgp"

Decrypt File

// Load keys
FileInfo privateKey = new FileInfo(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(privateKey, "password");

// Reference input/output files
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\encryptedContent.pgp");
FileInfo decryptedFile = new FileInfo(@"C:\TEMP\Content\decrypted.txt");

// Decrypt
PGP pgp = new PGP(encryptionKeys);
await pgp.DecryptAsync(inputFile, decryptedFile);

Decrypt Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream privateKeyStream = new FileStream(@"C:\TEMP\Keys\private.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(privateKeyStream, "password");

PGP pgp = new PGP(encryptionKeys);

// Reference input/output files
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\encryptedContent.pgp", FileMode.Open))
using (Stream outputFileStream = File.Create(@"C:\TEMP\Content\decrypted.txt"))
	// Decrypt
	await pgp.DecryptAsync(inputFileStream, outputFileStream);

Decrypt String

// Load keys
string privateKey = File.ReadAllText(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(privateKey, "password");

PGP pgp = new PGP(encryptionKeys);

// Decrypt
string decryptedContent = await pgp.DecryptAsync("String to decrypt");

Verify

Verify that the file, stream or string was signed by the matching private key of the counterparty.

gpg --verify "C:\TEMP\Content\signed.pgp"

Verify File

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

// Reference input
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\signedContent.pgp");

// Verify
PGP pgp = new PGP(encryptionKeys);
bool verified = await pgp.VerifyAsync(inputFile);

Verify Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(publicKeyStream);

PGP pgp = new PGP(encryptionKeys);

// Reference input file
bool verified;
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\encryptedContent.pgp", FileMode.Open))
	// Verify
	verified = await pgp.VerifyAsync(inputFileStream);

Verify String

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

PGP pgp = new PGP(encryptionKeys);

// Verify
bool verified = await pgp.VerifyAsync("String to verify");

Verify and Read

Verify that the file, stream was signed by the matching private key of the counterparty. This is an overload of the Verify method that takes an additional output argument. Please note that this is not available for the string based method.

Verify And Read File

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

// Reference input
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\signedContent.pgp");
FileInfo outputFile = new FileInfo(@"C:\TEMP\Content\decryptedContent.txt");

// Verify and read
PGP pgp = new PGP(encryptionKeys);
bool verified = await pgp.VerifyAsync(inputFile, outputFile);

Verify And Read Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(publicKeyStream);

PGP pgp = new PGP(encryptionKeys);

// Reference input file
bool verified;
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\encryptedContent.pgp", FileMode.Open))
using (FileStream outputFileStream = new FileStream(@"C:\TEMP\Content\decryptedContent.pgp", FileMode.Open))
	// Verify and read
	verified = await pgp.VerifyAsync(inputFileStream);

Verify And Read String

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

PGP pgp = new PGP(encryptionKeys);

// Verify and read
string output = string.Empty;
bool verified = await pgp.VerifyAsync("String to verify", output);

Verify Clear

Verify that the clear signed file or stream was signed by the matching private key of the counterparty.

gpg --verify "C:\TEMP\Content\clearSigned.pgp"

Verify Clear File

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

// Reference input
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\signedContent.pgp");

// Verify
PGP pgp = new PGP(encryptionKeys);
bool verified = await pgp.VerifyClearAsync(inputFile);

Verify Clear Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
	encryptionKeys = new EncryptionKeys(publicKeyStream);

PGP pgp = new PGP(encryptionKeys);

// Reference input file
bool verified;
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\encryptedContent.pgp", FileMode.Open))
	// Verify
	verified = await pgp.VerifyClearAsync(inputFileStream);

Verify Clear String

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

PGP pgp = new PGP(encryptionKeys);

// Verify
bool verified = await pgp.VerifyClearAsync("String to verify");

Verify and Read Clear

Verify that the clear signed file or stream was signed by the matching private key of the counterparty. This is an overload of the VerifyClear method that takes an additional output argument.

Verify And Read Clear File

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

// Reference input
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\signedContent.pgp");
FileInfo outputFile = new FileInfo(@"C:\TEMP\Content\decryptedContent.txt");

// Verify and read
PGP pgp = new PGP(encryptionKeys);
bool verified = await pgp.VerifyClearAsync(inputFile, outputFile);

Verify And Read Clear Stream

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
    encryptionKeys = new EncryptionKeys(publicKeyStream);

PGP pgp = new PGP(encryptionKeys);

// Reference input file
bool verified;
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\encryptedContent.pgp", FileMode.Open))
using (FileStream outputFileStream = new FileStream(@"C:\TEMP\Content\decryptedContent.pgp", FileMode.Open))
    // Verify and read
    verified = await pgp.VerifyClearAsync(inputFileStream);

Verify And Read Clear String

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey);

PGP pgp = new PGP(encryptionKeys);

// Verify and read
string output = string.Empty;
bool verified = await pgp.VerifyClearAsync("String to verify", output);

Decrypt and Verify

Decrypt and then verify the provided encrypted and signed file, stream or string. Usually your counterparty will encrypt with your public key and sign with their private key so you can decrypt with your private key and verify with their public key.

The DecryptAndVerify methods will only work with files that have been encrypted and signed using the EncryptAndSign methods. This is because the signature is included within the encrypted message rather than being appended to the encrypted message. If a file is first encrypted using an Encrypt method and then signed using a Sign method then the signature will be appended to the encrypted message rather than embedded within it and the DecryptAndVerify methods will not be able to verify the signature.

gpg --output "C:\TEMP\Content\encryptedAndSigned.pgp" --decrypt "C:\TEMP\Content\decryptedAndVerified.txt"

Decrypt File And Verify

// Load keys
FileInfo publicKey = new FileInfo(@"C:\TEMP\Keys\public.asc");
FileInfo privateKey = new FileInfo(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey, privateKey, "password");

// Reference input/output files
FileInfo inputFile = new FileInfo(@"C:\TEMP\Content\encryptedSigned.pgp");
FileInfo outputFile = new FileInfo(@"C:\TEMP\Content\content.txt");

// Decrypt and Verify
PGP pgp = new PGP(encryptionKeys);
await pgp.DecryptAndVerifyAsync(inputFile, outputFile);

Decrypt Stream And Verify

// Load keys
EncryptionKeys encryptionKeys;
using (Stream publicKeyStream = new FileStream(@"C:\TEMP\Keys\public.asc", FileMode.Open))
using (Stream privateKeyStream = new FileStream(@"C:\TEMP\Keys\private.asc", FileMode.Open))
    encryptionKeys = new EncryptionKeys(publicKeyStream, privateKeyStream, "password");

PGP pgp = new PGP(encryptionKeys);

// Reference input/output files
using (FileStream inputFileStream = new FileStream(@"C:\TEMP\Content\encryptedSigned.pgp", FileMode.Open))
using (Stream outputFileStream = File.Create(@"C:\TEMP\Content\content.txtp"))
    // Decrypt and Verify
    await pgp.DecryptAndVerifyAsync(inputFileStream, outputFileStream);

Decrypt String And Verify

// Load keys
string publicKey = File.ReadAllText(@"C:\TEMP\Keys\public.asc");
string privateKey = File.ReadAllText(@"C:\TEMP\Keys\private.asc");
EncryptionKeys encryptionKeys = new EncryptionKeys(publicKey, privateKey, "password");

PGP pgp = new PGP(encryptionKeys);

// Decrypt and Verify
string encryptedSignedContent = await pgp.DecryptAndVerifyAsync("String to decrypt and verify");

Key Management

EncryptionKeys picks the best key for each job automatically: the strongest encryption-capable, unexpired, unrevoked key from each supplied key ring (newest first among equals), and every key and subkey is available for signature verification. Two tools change that behaviour when the automatic choice is not what you need.

EncryptionKeysBuilder

A fluent alternative to the EncryptionKeys constructors. Its main advantage is combining multiple private keys, each with its own passphrase — useful when decrypting messages that may be encrypted to any of several keys you hold.

EncryptionKeys encryptionKeys = new EncryptionKeysBuilder()
	.WithPublicKey(new FileInfo(@"C:\TEMP\Keys\recipient.asc"))
	.WithPrivateKey(new FileInfo(@"C:\TEMP\Keys\private1.asc"), "passphrase1")
	.WithPrivateKey(new FileInfo(@"C:\TEMP\Keys\private2.asc"), "passphrase2")
	.Build();

PGP pgp = new PGP(encryptionKeys);

UseEncryptionKey

Selects a specific key (by key id) as the encryption key, instead of the automatically chosen one. This is also the override for encrypting to an expired or revoked key, which the automatic selection refuses. Throws MissingKeyException when no supplied key ring contains an encryption key with that id.

EncryptionKeys encryptionKeys = new EncryptionKeys(new FileInfo(@"C:\TEMP\Keys\public.asc"));
encryptionKeys.UseEncryptionKey(0x123456789ABCDEF0);

PGP pgp = new PGP(encryptionKeys);

The same selection is available at construction via the builder's WithPreferredEncryptionKeyId(keyId).

Settings

The PGP object contains a variety of settings properties that can be used to determine how files are encrypted.

CompressionAlgorithm

The compression algorithm to be used on the message. This is applied prior to encryption, either to the message or the signed message.

Uncompressed
Zip - Default
ZLib
BZip2

SymmetricKeyAlgorithm

The private key encryption algorithm.

Null
Idea
TripleDes
Cast5
Blowfish
Safer
Des
Aes128
Aes192
Aes256 - Default
Twofish
Camellia128
Camellia192
Camellia256

PgpSignatureType

The type of signature to be used for file signing.

BinaryDocument
CanonicalTextDocument
StandAlone
DefaultCertification - Default
NoCertification
CasualCertification
PositiveCertification
SubkeyBinding
PrimaryKeyBinding
DirectKey
KeyRevocation
SubkeyRevocation
CertificationRevocation
Timestamp

PublicKeyAlgorithm

The algorithm used for the master key created by GenerateKey.

GenerateKey produces a certify/sign master key plus a matching encryption subkey, so the master key algorithm only needs to be capable of signing. The encryption subkey algorithm is chosen automatically:

PublicKeyAlgorithm	Master key	Encryption subkey
RsaGeneral - Default	RSA	RSA
RsaEncrypt	RSA	RSA
RsaSign	RSA	RSA
EdDsa	Ed25519	X25519 ECDH
ECDsa	NIST P-256	NIST P-256 ECDH
Dsa	DSA	RSA

Any other value (ECDH, ElGamalEncrypt, ElGamalGeneral, DiffieHellman) throws NotSupportedException, as those algorithms cannot sign or certify and so cannot be used for a master key. ECDH is still used as a subkey algorithm via the pairings above.

Two notes on Dsa:

DSA is paired with an RSA encryption subkey rather than the traditional ElGamal one. BouncyCastle's ElGamal parameter generation takes over two minutes at 2048 bits and considerably longer at the default strength, which would make key generation appear to hang. The subkey algorithm does not have to relate to the master's, and gpg accepts an RSA encryption subkey under a DSA primary key.
DSA strengths of 512-1024 bits must be a multiple of 64 (a BouncyCastle constraint); larger strengths are generated with a 256-bit subgroup per FIPS 186-3. An unusable strength now raises a descriptive ArgumentOutOfRangeException rather than the opaque BouncyCastle "size must be from 512 - 1024 and a multiple of 64" error reported in #285.

FileType

Encoding to be used for the output file.

Binary - Default
Text
UTF8

HashAlgorithmTag

The hash algorithm to be used by the signature.

MD5
Sha1
RipeMD160
DoubleSha
MD2
Tiger192
Haval5pass160
Sha256 - Default
Sha384
Sha512
Sha224

During GenerateKey this value is also used for the key's self-certification, where some algorithms require a minimum digest size: 256 bits for EdDsa and ECDsa, and at least the subgroup size for Dsa (256 bits above 1024-bit keys, otherwise 160). If the requested hash is shorter than the key algorithm requires, SHA-256 is used for the certification instead — a shorter digest would produce a self-certification that other implementations may reject, and some combinations (MD5 with ECDsa or Dsa) cannot be signed by BouncyCastle at all. RSA keys have no such requirement and always use the requested hash.

IgnoreIntegrityCheckFailure

When true, a failed modification detection (MDC) integrity check during Decrypt or DecryptAndVerify is tolerated instead of throwing MessageIntegrityException. Equivalent to gpg --ignore-mdc-error. Defaults to false; only enable it to recover data from a message you have other reasons to trust, since a failed check means the ciphertext was modified.

PGP pgp = new PGP(encryptionKeys) { IgnoreIntegrityCheckFailure = true };

TextEncoding

The text encoding used by the string based overloads when converting between strings and bytes. Defaults to UTF-8 without a byte order mark, which round trips any .NET string. Set it when a counterparty produces or expects text in a specific legacy encoding — the encoding must match on both the encrypting and decrypting side. The stream and file overloads are unaffected, as they never reinterpret bytes as text.

PGP pgp = new PGP(encryptionKeys) { TextEncoding = Encoding.GetEncoding(1253) };

Exceptions

Operations throw specific exception types, all deriving from PgpCoreException (which derives from System.Exception):

Exception	Thrown when
`NotEncryptedDataException`	`Decrypt` input is not PGP encrypted data — plain text, signed-only, or clear-signed content.
`UnsupportedAeadException`	The message uses AEAD (OCB) encryption, which the referenced BouncyCastle version cannot read (#219).
`IncorrectPassphraseException`	The supplied passphrase does not unlock the private key.
`InvalidKeyMaterialException`	Key material could not be parsed, or contained no usable keys.
`MessageIntegrityException`	The message failed its modification detection (MDC) check — see IgnoreIntegrityCheckFailure.
`MissingKeyException`	An operation needs a key that was not supplied (e.g. `UseEncryptionKey` with an unknown key id).
`NoEncryptionKeyException`	No usable encryption key was found — including when the only candidates are expired or revoked.
`NoSigningKeyException`	No key suitable for signing was found in the supplied private key material.
`NoDecryptionKeyException`	None of the supplied private keys match any key the message is encrypted to (the message's key ids are listed).

PgpException (BouncyCastle's type) is still thrown for signature verification failures, e.g. "Failed to verify file." from DecryptAndVerify.

Name		Name	Last commit message	Last commit date
Latest commit History 684 Commits
.github/workflows		.github/workflows
PgpCore.Tests		PgpCore.Tests
PgpCore		PgpCore
.editorconfig		.editorconfig
.gitattributes		.gitattributes
.gitignore		.gitignore
CLAUDE.md		CLAUDE.md
LICENSE		LICENSE
PgpCore.sln		PgpCore.sln
README.md		README.md

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PgpCore

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Upgrading to v8.0

Azure Function Example

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