EdDSA C# Reference Documentation

EdDSA

Current Version: 11.5.0

Chilkat.EdDSA

Generate Ed25519 keys, sign data, verify signatures, and compute shared secrets.

Chilkat.EdDSA is the Chilkat class for Ed25519-based EdDSA operations. It can generate Ed25519 private keys, sign data contained in BinData, verify encoded signatures with public keys, and compute encoded shared secrets from compatible private/public key pairs. It supports the Ed25519, Ed25519ph, and Ed25519ctx variants, with optional context bytes supplied as a hex string when the selected variant requires them.

Generate Ed25519 keys

Create Ed25519 private keys for signing, verification, and compatible key-agreement workflows.

Sign BinData

Sign binary data directly from a Chilkat.BinData object using an Ed25519 private key.

Verify signatures

Verify encoded EdDSA signatures using the corresponding public key and the original message data.

Ed25519 variants

Use Ed25519, Ed25519ph, or Ed25519ctx depending on the protocol or interoperability requirements.

Context support

Supply optional context bytes as a hex string for workflows that use the Ed25519ctx or related context-aware signing modes.

Shared-secret output

Compute encoded shared secrets from compatible private and public key pairs for protocols that require this operation.

Common pattern: Generate or load an Ed25519 key, choose the required EdDSA variant, provide context bytes when needed, then sign or verify the BinData content. For shared-secret workflows, compute the encoded secret and pass it through the key derivation or formatting step required by the protocol.

Object Creation

Chilkat.EdDSA obj = new Chilkat.EdDSA();

Properties

Algorithm
public string Algorithm {get; set; }
Introduced in version 9.5.0.91

Selects the Ed25519 signature variant used by SignBdENC and VerifyBdENC. The default is Ed25519.

ValueBehaviorContext
Ed25519The standard pure Ed25519 signature scheme. The complete message is signed directly by the Ed25519 algorithm.A context is not part of this variant and should be empty.
Ed25519ctxPure Ed25519 with domain separation supplied by a context string.The context should normally be nonempty and must match exactly during verification.
Ed25519phPrehash Ed25519. Chilkat first hashes the message with SHA-512 as defined for this variant.May be empty or contain up to 255 context bytes; it must match exactly during verification.
Interoperability requirement: The signer and verifier must select the same variant. An Ed25519ph signature cannot be verified as ordinary Ed25519, even if the same key and message are used.
Scope: This property selects a signing variant; it does not change the type of key generated by GenEd25519Key and does not affect SharedSecretENC.

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Context
public string Context {get; set; }
Introduced in version 9.5.0.91

Gets or sets the context bytes used by the Ed25519ctx and Ed25519ph signature variants. Supply the bytes as a hexadecimal string. The default is an empty string.

A context may contain at most 255 bytes, which corresponds to at most 510 hexadecimal characters. The same context bytes must be supplied byte-for-byte when verifying the signature. An invalid hexadecimal value or an oversized context causes the signing or verification operation to fail.

Domain separation: A context is a public protocol label that separates signatures created for different purposes, applications, or message types. It is not a password, secret key, salt, or part of the message payload.
Algorithm interaction: Use this property only when Algorithm is Ed25519ctx or Ed25519ph. Standard Ed25519 does not include a context.

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DebugLogFilePath
public string DebugLogFilePath {get; set; }

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

  • A timeout property set to 0, indicating an infinite timeout.
  • A hang occurring within an event callback in the application code.
  • An internal bug in the Chilkat code causing the hang.

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LastErrorHtml
public string LastErrorHtml {get; }

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorText
public string LastErrorText {get; }

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorXml
public string LastErrorXml {get; }

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastMethodSuccess
public bool LastMethodSuccess {get; set; }

Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

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VerboseLogging
public bool VerboseLogging {get; set; }

If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
public string Version {get; }

Version of the component/library, such as "10.1.0"

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Methods

GenEd25519Key
public bool GenEd25519Key(Prng prng, PrivateKey privKey);
Introduced in version 9.5.0.83

Generates a new Ed25519 key pair using prng as the source of cryptographically secure random bytes. On success, the generated private key and its corresponding public key are stored in the existing PrivateKey object passed in privKey.

Returns true on success and false on failure. If the method fails, inspect LastErrorText for details.

Ed25519 key size: Ed25519 key generation begins with a 32-byte private-key seed from which the public key is derived. Exported PEM, DER, JWK, or other key formats may contain additional structure and metadata, so their serialized size is not necessarily 32 bytes.
Protect the private key: The generated private key can create signatures on behalf of its owner. Store it securely and disclose only the corresponding public key.

Returns true for success, false for failure.

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SharedSecretENC
public string SharedSecretENC(PrivateKey privkey, PublicKey pubkey, string encoding);
Introduced in version 9.5.0.83

Computes a 32-byte X25519 shared secret from the private key in privkey and the peer's public key in pubkey. The resulting bytes are returned as text using the binary encoding named by encoding, such as hex, hexlower, or base64.

Each participant supplies its own private key and the other participant's public key. When Alice computes the secret from Alice's private key and Bob's public key, and Bob computes it from Bob's private key and Alice's public key, both obtain the same result.

X25519, not an EdDSA signature operation: This method performs Curve25519 Diffie-Hellman key agreement. It is separate from the Ed25519, Ed25519ctx, and Ed25519ph signature variants, so the Algorithm and Context properties do not apply.
Do not normally use the raw secret directly: A protocol should pass the shared secret through its specified key-derivation function and should authenticate the participants' public keys. Key agreement by itself does not establish the peer's identity.

This is a string-returning method. Check LastMethodSuccess before using the returned value; on failure, inspect LastErrorText.

Returns null on failure

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SignBdENC
public string SignBdENC(BinData bd, string encoding, PrivateKey privkey);
Introduced in version 9.5.0.83

Creates an EdDSA signature over the exact byte sequence contained in bd, using the Ed25519 private key in privkey. The 64-byte signature is returned as text using the binary encoding named by encoding, such as hex, hexlower, or base64.

The selected Algorithm and Context properties determine whether the operation uses Ed25519, Ed25519ctx, or Ed25519ph. For Ed25519ph, pass the original message bytes in bd; Chilkat performs the required SHA-512 prehash as part of the Ed25519ph operation.

Deterministic signatures: Ed25519 signatures do not require a caller-supplied per-message random number. With the same private key, message, algorithm variant, and context, the signature is deterministic.
Ed25519ph is a distinct variant: It is not equivalent to hashing the message yourself and then signing that digest with ordinary Ed25519. Ed25519ph includes variant-specific domain separation.

This is a string-returning method. Check LastMethodSuccess before using the returned value; on failure, inspect LastErrorText.

Returns null on failure

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VerifyBdENC
public bool VerifyBdENC(BinData bd, string encodedSig, string enocding, PublicKey pubkey);
Introduced in version 9.5.0.83

Verifies the encoded EdDSA signature in encodedSig against the exact byte sequence contained in bd, using the Ed25519 public key in pubkey. enocding names the binary encoding of encodedSig, such as hex, hexlower, or base64.

The verifier must use the same Algorithm and Context values that were used to create the signature. Any change to the message, signature, public key, algorithm variant, or context causes verification to fail.

Returns true only when the signature is valid. Returns false for an invalid signature or an operational error, such as malformed encoded input, an unsupported encoding, or an unsuitable key. Inspect LastErrorText for diagnostic information.

Trust remains an application decision: A valid signature proves that the message matches the supplied public key. The application must still establish that the public key belongs to the expected signer.

Returns true for success, false for failure.

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