diff --git a/build.sbt b/build.sbt
index 38ee008..fd1fa03 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,4 +1,4 @@
-val scala3: String = "3.8.1"
+val scala3: String = "3.8.2"
 
 ThisBuild / scalaVersion  := scala3
 ThisBuild / versionScheme := Some("semver-spec")
@@ -33,11 +33,12 @@ val Deps = new {
   }
 
   val Gs = new {
-    val Datagen: ModuleID = "gs" %% "gs-datagen-core-v0" % "0.1.1"
+    val Datagen: ModuleID = "gs" %% "gs-datagen-core-v0" % "0.4.1"
   }
 
   val BouncyCastle = new {
     val Provider: ModuleID = "org.bouncycastle" % "bcprov-jdk18on" % "1.83"
+    val PKIX: ModuleID     = "org.bouncycastle" % "bcpkix-jdk18on" % "1.83"
   }
 
   val MUnit: ModuleID = "org.scalameta" %% "munit" % "1.2.2"
@@ -52,7 +53,7 @@ lazy val testSettings = Seq(
 
 lazy val `gs-crypto` = project
   .in(file("."))
-  .aggregate(core, argon2, rsa)
+  .aggregate(core, argon2, rsa, eddsa)
   .settings(noPublishSettings)
   .settings(name := s"${gsProjectName.value}-v${semVerMajor.value}")
 
@@ -65,7 +66,8 @@ lazy val core = project
   )
   .settings(
     libraryDependencies ++= Seq(
-      Deps.Cats.Effect
+      Deps.Cats.Effect,
+      Deps.BouncyCastle.PKIX
     )
   )
 
@@ -97,3 +99,18 @@ lazy val rsa = project
       Deps.Cats.Effect
     )
   )
+
+lazy val eddsa = project
+  .in(file("modules/eddsa"))
+  .dependsOn(core)
+  .settings(sharedSettings)
+  .settings(testSettings)
+  .settings(
+    name := s"${gsProjectName.value}-eddsa-v${semVerMajor.value}"
+  )
+  .settings(
+    libraryDependencies ++= Seq(
+      Deps.Cats.Effect,
+      Deps.BouncyCastle.Provider
+    )
+  )
diff --git a/modules/core/src/main/scala/gs/crypto/v0/Base64Decoder.scala b/modules/core/src/main/scala/gs/crypto/v0/Base64Decoder.scala
index 97680c6..271c6ff 100644
--- a/modules/core/src/main/scala/gs/crypto/v0/Base64Decoder.scala
+++ b/modules/core/src/main/scala/gs/crypto/v0/Base64Decoder.scala
@@ -3,9 +3,12 @@ package gs.crypto.v0
 import java.{util => ju}
 
 /** Implementation of [[Decoder]] for Base64 strings.
+  *
+  * Supports base64-url decoding as well.
   */
 object Base64Decoder extends Decoder[B64]:
-  private lazy val d: ju.Base64.Decoder = ju.Base64.getDecoder()
+  private lazy val d: ju.Base64.Decoder  = ju.Base64.getDecoder()
+  private lazy val du: ju.Base64.Decoder = ju.Base64.getUrlDecoder()
 
   /** @inheritDocs
     */
@@ -21,3 +24,13 @@ object Base64Decoder extends Decoder[B64]:
     */
   def decodeUnsafe(input: String): Array[Byte] =
     d.decode(input)
+
+  /** Decode the base64-url encoded input.
+    *
+    * @param input
+    *   The base64-url encoded data.
+    * @return
+    *   The decoded bytes.
+    */
+  def decodeUrl(input: B64Url): Array[Byte] =
+    du.decode(input.data)
diff --git a/modules/core/src/main/scala/gs/crypto/v0/Base64Encoder.scala b/modules/core/src/main/scala/gs/crypto/v0/Base64Encoder.scala
index 525fc72..24bcaf3 100644
--- a/modules/core/src/main/scala/gs/crypto/v0/Base64Encoder.scala
+++ b/modules/core/src/main/scala/gs/crypto/v0/Base64Encoder.scala
@@ -5,9 +5,12 @@ import java.nio.charset.StandardCharsets
 import java.util.Base64
 
 /** Implementation of [[Encoder]] for Base64.
+  *
+  * Supports base64-url encoding as well.
   */
 object Base64Encoder extends Encoder[B64]:
-  private lazy val e: Base64.Encoder = Base64.getEncoder()
+  private lazy val e: Base64.Encoder  = Base64.getEncoder()
+  private lazy val eu: Base64.Encoder = Base64.getUrlEncoder()
 
   /** @inheritDocs
     */
@@ -21,3 +24,28 @@ object Base64Encoder extends Encoder[B64]:
     charset: Charset = StandardCharsets.UTF_8
   ): B64 =
     encode(input.getBytes(charset))
+
+  /** Encode the given bytes using base64-url.
+    *
+    * @param input
+    *   The input data.
+    * @return
+    *   The base64-url-encoded string.
+    */
+  def encodeUrl(input: Array[Byte]): B64Url =
+    B64Url(eu.encodeToString(input))
+
+  /** Encode the given bytes using base64-url.
+    *
+    * @param input
+    *   The input data.
+    * @param charset
+    *   The character set of the input data.
+    * @return
+    *   The base64-url-encoded string.
+    */
+  def encodeUrl(
+    input: String,
+    charset: Charset = StandardCharsets.UTF_8
+  ): B64Url =
+    encodeUrl(input.getBytes(charset))
diff --git a/modules/core/src/main/scala/gs/crypto/v0/BaseKeyLoader.scala b/modules/core/src/main/scala/gs/crypto/v0/BaseKeyLoader.scala
new file mode 100644
index 0000000..f8a8afa
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/BaseKeyLoader.scala
@@ -0,0 +1,122 @@
+package gs.crypto.v0
+
+import cats.effect.Sync
+import cats.syntax.all.*
+import java.security.PrivateKey
+import java.security.PublicKey
+
+/** Base implementation for [[KeyLoader]] that provides standard parsing
+  * functionality.
+  */
+abstract class BaseKeyLoader[F[_]: Sync] extends KeyLoader[F]:
+
+  def loadPublicKey(
+    location: String,
+    algorithm: String
+  ): F[Either[KeyLoadError, PublicKey]] =
+    loadKey(location).flatMap {
+      case Left(err) => Sync[F].pure(Left(err))
+      case Right(key) =>
+        KeyLoader.loadPublicKey[F](key, algorithm).map(Right(_))
+    }
+
+  def loadPrivateKey(
+    location: String,
+    algorithm: String
+  ): F[Either[KeyLoadError, PrivateKey]] =
+    loadKey(location).flatMap {
+      case Left(err) => Sync[F].pure(Left(err))
+      case Right(key) =>
+        KeyLoader.loadPrivateKey[F](key, algorithm).map(Right(_))
+    }
+
+    /** @return
+      *   The key loader configuration.
+      */
+
+  def config: BaseKeyLoader.Config
+
+  protected def prepareKey(base: String): Either[KeyLoadError, Array[Byte]] =
+    scala.util
+      .Try {
+        config.decoder.decode(trim(collapse(unwrap(base))))
+      }
+      .toEither
+      .left
+      .map(_ => KeyLoadError.DecodingFailure(config.encodingName))
+
+  private def unwrap(base: String): String =
+    config.wrappers.foldLeft(base) {
+      (
+        acc,
+        w
+      ) => acc.replace(w, "")
+    }
+
+  private def collapse(base: String): String =
+    if config.shouldCollapse then base.replace("\n", "") else base
+
+  private def trim(base: String): String =
+    if config.shouldTrim then base.trim() else base
+
+object BaseKeyLoader:
+
+  /** Configuration for loading keys.
+    *
+    * @param wrappers
+    *   Values that wrap keys and must be removed.
+    * @param shouldCollapse
+    *   Whether newlines should be collapsed.
+    * @param shouldTrim
+    *   Whether the string data should be trimmed.
+    * @param encodingName
+    *   The name of the encoding.
+    * @param decoder
+    *   The decoder to be used on the pre-processed input.
+    */
+  case class Config(
+    wrappers: List[String],
+    shouldCollapse: Boolean,
+    shouldTrim: Boolean,
+    encodingName: String,
+    decoder: Decoder[String]
+  )
+
+  /** Default configuration values that work in most cases.
+    */
+  object Defaults:
+
+    /** By default, generic begin/end public/private key wrappers are included.
+      */
+    val Wrappers: List[String] = List(
+      "-----BEGIN PUBLIC KEY-----",
+      "-----END PUBLIC KEY-----",
+      "-----BEGIN PRIVATE KEY-----",
+      "-----END PRIVATE KEY-----"
+    )
+
+    /** By default, stringified key data has newlines removed.
+      */
+    val ShouldCollapse: Boolean = true
+
+    /** By default, stringified key data is trimmed.
+      */
+    val ShouldTrim: Boolean = true
+
+    /** The default encoding name is 'base64'.
+      */
+    val EncodingName: String = "base64"
+
+    /** The default configuration handles standard wrapped, base64-encoded keys.
+      */
+    val Config: BaseKeyLoader.Config = BaseKeyLoader.Config(
+      wrappers = Wrappers,
+      shouldCollapse = ShouldCollapse,
+      shouldTrim = ShouldTrim,
+      encodingName = EncodingName,
+      decoder = s => Base64Decoder.decodeUnsafe(s)
+    )
+
+  end Defaults
+
+end BaseKeyLoader
diff --git a/modules/core/src/main/scala/gs/crypto/v0/Encoded.scala b/modules/core/src/main/scala/gs/crypto/v0/Encoded.scala
index a80629e..98c615d 100644
--- a/modules/core/src/main/scala/gs/crypto/v0/Encoded.scala
+++ b/modules/core/src/main/scala/gs/crypto/v0/Encoded.scala
@@ -23,6 +23,11 @@ trait Encoded:
     *   The encoded data.
     */
 
+/** Represents Base64-encoded data.
+  *
+  * @param data
+  *   The encoded data.
+  */
 final class B64(
   val data: String
 ) extends Encoded:
@@ -63,6 +68,51 @@ object B64:
 
 end B64
 
+/** Represents Base64-url-encoded data.
+  *
+  * @param data
+  *   The encoded data.
+  */
+final class B64Url(
+  val data: String
+) extends Encoded:
+  /** @inheritDocs
+    */
+  def decode(): Array[Byte] = Base64Decoder.decodeUrl(this)
+
+  /** @inheritDocs
+    */
+  override def equals(obj: Any): Boolean =
+    obj match
+      case other: B64Url => data == other.data
+
+  /** @inheritDocs
+    */
+  override def hashCode(): Int = data.hashCode()
+
+  /** @inheritDocs
+    */
+  override def toString(): String = data
+
+object B64Url:
+
+  /** Instantiate [[B64Url]] from the given string.
+    *
+    * This function does NOT validate the input.
+    *
+    * @param data
+    *   The encoded data.
+    * @return
+    *   The new [[B64Url]] instance.
+    */
+  def apply(
+    data: String
+  ): B64Url = new B64Url(data)
+
+  given CanEqual[B64Url, B64Url] = CanEqual.derived
+
+end B64Url
+
 /** Represents Hex-encoded data.
   *
   * @param data
diff --git a/modules/core/src/main/scala/gs/crypto/v0/FileKeyLoader.scala b/modules/core/src/main/scala/gs/crypto/v0/FileKeyLoader.scala
new file mode 100644
index 0000000..22d27fa
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/FileKeyLoader.scala
@@ -0,0 +1,30 @@
+package gs.crypto.v0
+
+import cats.effect.Sync
+import cats.syntax.all.*
+import java.nio.file.Files
+import java.nio.file.Path
+
+/** Implementation of [[KeyLoader]] that loads keys from encoded string files.
+  *
+  * @param config
+  *   The key loader configuration.
+  * @param charset
+  *   The expected character set for the loaded file.
+  */
+class FileKeyLoader[F[_]: Sync](
+  val config: BaseKeyLoader.Config
+) extends BaseKeyLoader[F]:
+
+  /** @inheritDocs
+    */
+  override def loadKey(
+    location: String
+  ): F[Either[KeyLoadError, Array[Byte]]] =
+    val p = Path.of(location)
+    Sync[F].delay(Files.isRegularFile(p)).flatMap {
+      case false =>
+        Sync[F].pure(Left(KeyLoadError.PathNotRegularFile(p, location)))
+      case true =>
+        Sync[F].delay(Files.readString(p)).map(prepareKey)
+    }
diff --git a/modules/core/src/main/scala/gs/crypto/v0/KeyLoadError.scala b/modules/core/src/main/scala/gs/crypto/v0/KeyLoadError.scala
new file mode 100644
index 0000000..8e8e1e9
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/KeyLoadError.scala
@@ -0,0 +1,16 @@
+package gs.crypto.v0
+
+import java.nio.file.Path
+
+sealed trait KeyLoadError
+
+object KeyLoadError:
+
+  case class PathNotRegularFile(
+    path: Path,
+    location: String
+  ) extends KeyLoadError
+
+  case class DecodingFailure(encodedFormat: String) extends KeyLoadError
+
+end KeyLoadError
diff --git a/modules/core/src/main/scala/gs/crypto/v0/KeyLoader.scala b/modules/core/src/main/scala/gs/crypto/v0/KeyLoader.scala
new file mode 100644
index 0000000..c0b8aba
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/KeyLoader.scala
@@ -0,0 +1,61 @@
+package gs.crypto.v0
+
+import cats.effect.Sync
+import java.security.KeyFactory
+import java.security.PrivateKey
+import java.security.PublicKey
+import java.security.spec.PKCS8EncodedKeySpec
+import java.security.spec.X509EncodedKeySpec
+
+/** Interface for loading keys (e.g. public/private keys) into memory.
+  */
+trait KeyLoader[F[_]]:
+  /** Load the key from the given location. This gets the raw bytes, but does
+    * not handle _any_ standard encodings such as PKCS8 or X509. These are
+    * handled by helper functions (static) or [[BaseKeyLoader]].
+    *
+    * @param location
+    *   The location of the key.
+    * @return
+    *   The key's raw bytes - ready for further decoding.
+    */
+  def loadKey(location: String): F[Either[KeyLoadError, Array[Byte]]]
+
+object KeyLoader:
+
+  def stringLoader[F[_]: Sync](
+    config: BaseKeyLoader.Config = BaseKeyLoader.Defaults.Config
+  ): StringKeyLoader[F] =
+    new StringKeyLoader(config)
+
+  def fileLoader[F[_]: Sync](
+    config: BaseKeyLoader.Config = BaseKeyLoader.Defaults.Config
+  ): FileKeyLoader[F] =
+    new FileKeyLoader(config)
+
+  def resourceLoader[F[_]: Sync](
+    config: BaseKeyLoader.Config = BaseKeyLoader.Defaults.Config
+  ): ResourceKeyLoader[F] =
+    new ResourceKeyLoader(config)
+
+  def loadPublicKey[F[_]: Sync](
+    publicKeyRawBytes: Array[Byte],
+    algorithm: String
+  ): F[PublicKey] =
+    Sync[F].delay {
+      val spec       = new X509EncodedKeySpec(publicKeyRawBytes)
+      val keyFactory = KeyFactory.getInstance(algorithm)
+      keyFactory.generatePublic(spec)
+    }
+
+  def loadPrivateKey[F[_]: Sync](
+    privateKeyRawBytes: Array[Byte],
+    algorithm: String
+  ): F[PrivateKey] =
+    Sync[F].delay {
+      val spec       = new PKCS8EncodedKeySpec(privateKeyRawBytes)
+      val keyFactory = KeyFactory.getInstance(algorithm)
+      keyFactory.generatePrivate(spec)
+    }
+
+end KeyLoader
diff --git a/modules/core/src/main/scala/gs/crypto/v0/ResourceKeyLoader.scala b/modules/core/src/main/scala/gs/crypto/v0/ResourceKeyLoader.scala
new file mode 100644
index 0000000..afefa4d
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/ResourceKeyLoader.scala
@@ -0,0 +1,26 @@
+package gs.crypto.v0
+
+import cats.effect.Resource
+import cats.effect.Sync
+import scala.io.Source
+
+/** Implementation of [[KeyLoader]] that loads keys from encoded string files
+  * that exist as project resources.
+  *
+  * @param config
+  *   The key loader configuration.
+  */
+class ResourceKeyLoader[F[_]: Sync](
+  val config: BaseKeyLoader.Config
+) extends BaseKeyLoader[F]:
+
+  /** @inheritDocs
+    */
+  override def loadKey(
+    location: String
+  ): F[Either[KeyLoadError, Array[Byte]]] =
+    Resource
+      .make(Sync[F].delay(Source.fromResource(location)))(source =>
+        Sync[F].delay(source.close())
+      )
+      .use(source => Sync[F].delay(prepareKey(source.getLines().mkString)))
diff --git a/modules/core/src/main/scala/gs/crypto/v0/Signature.scala b/modules/core/src/main/scala/gs/crypto/v0/Signature.scala
new file mode 100644
index 0000000..dfb4b58
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/Signature.scala
@@ -0,0 +1,51 @@
+package gs.crypto.v0
+
+/** Represents a cryptographic signature. Opaque type for an array of bytes.
+  */
+opaque type Signature = Array[Byte]
+
+object Signature:
+
+  /** Instantiate a new signature from the given byte array.
+    *
+    * @param value
+    *   The signature value.
+    * @return
+    *   The signature bytes.
+    */
+  def apply(value: Array[Byte]): Signature = value
+
+  /** Instantiate a new signature from the given encoded string.
+    *
+    * @param value
+    *   The input data.
+    * @return
+    *   The new signature.
+    */
+  def fromEncoded(value: Encoded): Signature =
+    value.decode()
+
+  given CanEqual[Signature, Signature] = CanEqual.derived
+
+  extension (sig: Signature)
+    /** @return
+      *   The underlying byte array.
+      */
+    def unwrap(): Array[Byte] = sig
+
+    /** @return
+      *   This signature, encoded using base64.
+      */
+    def toBase64(): B64 = Base64Encoder.encode(sig)
+
+    /** @return
+      *   This signature, encoded using base64-url.
+      */
+    def toBase64Url(): B64Url = Base64Encoder.encodeUrl(sig)
+
+    /** @return
+      *   This signature, encoded using hex.
+      */
+    def toHex(): Hex = HexEncoder.encode(sig)
+
+end Signature
diff --git a/modules/core/src/main/scala/gs/crypto/v0/SignatureValidity.scala b/modules/core/src/main/scala/gs/crypto/v0/SignatureValidity.scala
new file mode 100644
index 0000000..f836aaf
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/SignatureValidity.scala
@@ -0,0 +1,50 @@
+package gs.crypto.v0
+
+/** Used to communicate the calculated validity of some [[Signature]].
+  *
+  * @param name
+  *   The enumeration name.
+  */
+sealed abstract class SignatureValidity(val name: String):
+
+  /** @inheritDocs
+    */
+  override def equals(obj: Any): Boolean =
+    obj match
+      case other: SignatureValidity => name == other.name
+      case _                        => false
+
+  /** @inheritDocs
+    */
+  override def hashCode(): Int = name.hashCode()
+
+  /** @inheritDocs
+    */
+  override def toString(): String = name
+
+object SignatureValidity:
+
+  /** Map a Boolean value to validity.
+    *
+    *   - True: Valid
+    *   - False: Invalid
+    *
+    * @param isValid
+    *   Whether the signature is valid or not.
+    * @return
+    *   The [[SignatureValidity]] selected for the given validity.
+    */
+  def apply(isValid: Boolean): SignatureValidity =
+    if isValid then Valid else Invalid
+
+  given CanEqual[SignatureValidity, SignatureValidity] = CanEqual.derived
+
+  /** The [[Signature]] is valid.
+    */
+  case object Valid extends SignatureValidity("valid")
+
+  /** The [[Signature]] is invalid.
+    */
+  case object Invalid extends SignatureValidity("invalid")
+
+end SignatureValidity
diff --git a/modules/core/src/main/scala/gs/crypto/v0/SignatureVerifier.scala b/modules/core/src/main/scala/gs/crypto/v0/SignatureVerifier.scala
new file mode 100644
index 0000000..5a497ee
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/SignatureVerifier.scala
@@ -0,0 +1,10 @@
+package gs.crypto.v0
+
+/** Used to verify cryptographic signatures.
+  */
+trait SignatureVerifier[F[_]]:
+
+  def verify(
+    signature: Signature,
+    data: Array[Byte]
+  ): F[SignatureValidity]
diff --git a/modules/core/src/main/scala/gs/crypto/v0/Signer.scala b/modules/core/src/main/scala/gs/crypto/v0/Signer.scala
new file mode 100644
index 0000000..3b387f3
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/Signer.scala
@@ -0,0 +1,30 @@
+package gs.crypto.v0
+
+import java.nio.charset.Charset
+import java.nio.charset.StandardCharsets
+
+/** Used to calculate cryptographic signatures.
+  */
+trait Signer[F[_]]:
+  /** Calculate a signature for the given data.
+    *
+    * @param data
+    *   The input data.
+    * @return
+    *   The calculated signature.
+    */
+  def sign(data: Array[Byte]): F[Signature]
+
+  /** Calculate a signature for the given data.
+    *
+    * @param data
+    *   The input data.
+    * @param charset
+    *   The character set of the input data.
+    * @return
+    *   The calculated signature.
+    */
+  def sign(
+    data: String,
+    charset: Charset = StandardCharsets.UTF_8
+  ): F[Signature]
diff --git a/modules/core/src/main/scala/gs/crypto/v0/StringKeyLoader.scala b/modules/core/src/main/scala/gs/crypto/v0/StringKeyLoader.scala
new file mode 100644
index 0000000..46cbc2a
--- /dev/null
+++ b/modules/core/src/main/scala/gs/crypto/v0/StringKeyLoader.scala
@@ -0,0 +1,15 @@
+package gs.crypto.v0
+
+import cats.effect.Sync
+
+/** Implementation of [[KeyLoader]] that loads keys directly from input strings.
+  *
+  * @param config
+  *   The key loader configuration.
+  */
+class StringKeyLoader[F[_]: Sync](
+  val config: BaseKeyLoader.Config
+) extends BaseKeyLoader[F]:
+
+  override def loadKey(location: String): F[Either[KeyLoadError, Array[Byte]]] =
+    Sync[F].delay(prepareKey(location))
diff --git a/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519.scala b/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519.scala
new file mode 100644
index 0000000..6ea343c
--- /dev/null
+++ b/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519.scala
@@ -0,0 +1,7 @@
+package gs.crypto.v0.eddsa
+
+object Ed25519:
+
+  val Algorithm: String = "Ed25519"
+
+end Ed25519
diff --git a/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519Signer.scala b/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519Signer.scala
new file mode 100644
index 0000000..7ae148b
--- /dev/null
+++ b/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519Signer.scala
@@ -0,0 +1,38 @@
+package gs.crypto.v0.eddsa
+
+import cats.effect.Sync
+import gs.crypto.v0.Signature
+import gs.crypto.v0.Signer
+import java.nio.charset.Charset
+import java.nio.charset.StandardCharsets
+import java.security.PrivateKey
+
+/** Implementation of [[Signer]] that uses the Ed25519 system to calculate
+  * signatures.
+  *
+  * See: [[Ed25519Verifier]]
+  *
+  * @param privateKey
+  *   The private key.
+  */
+final class Ed25519Signer[F[_]: Sync](
+  privateKey: PrivateKey
+) extends Signer[F]:
+
+  /** @inheritDocs
+    */
+  override def sign(data: Array[Byte]): F[Signature] =
+    Sync[F].delay {
+      val s = java.security.Signature.getInstance(Ed25519.Algorithm)
+      val _ = s.initSign(privateKey)
+      val _ = s.update(data)
+      Signature(s.sign())
+    }
+
+  /** @inheritDocs
+    */
+  override def sign(
+    data: String,
+    charset: Charset = StandardCharsets.UTF_8
+  ): F[Signature] =
+    sign(data.getBytes(charset))
diff --git a/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519Verifier.scala b/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519Verifier.scala
new file mode 100644
index 0000000..2107e0f
--- /dev/null
+++ b/modules/eddsa/src/main/scala/gs/crypto/v0/eddsa/Ed25519Verifier.scala
@@ -0,0 +1,32 @@
+package gs.crypto.v0.eddsa
+
+import cats.effect.Sync
+import gs.crypto.v0.Signature
+import gs.crypto.v0.SignatureValidity
+import gs.crypto.v0.SignatureVerifier
+import java.security.PublicKey
+
+/** Implementation of [[SignatureVerifier]] that uses the Ed25519 system to
+  * verify signatures.
+  *
+  * See: [[Ed25519Signer]]
+  *
+  * @param publicKey
+  *   The public key.
+  */
+final class Ed25519Verifier[F[_]: Sync](
+  publicKey: PublicKey
+) extends SignatureVerifier[F]:
+
+  /** @inheritDocs
+    */
+  override def verify(
+    signature: Signature,
+    data: Array[Byte]
+  ): F[SignatureValidity] =
+    Sync[F].delay {
+      val s = java.security.Signature.getInstance(Ed25519.Algorithm)
+      val _ = s.initVerify(publicKey)
+      val _ = s.update(data)
+      SignatureValidity(s.verify(signature.unwrap()))
+    }
diff --git a/modules/eddsa/src/test/resources/private.pem b/modules/eddsa/src/test/resources/private.pem
new file mode 100644
index 0000000..6afc843
--- /dev/null
+++ b/modules/eddsa/src/test/resources/private.pem
@@ -0,0 +1,3 @@
+-----BEGIN PRIVATE KEY-----
+MC4CAQAwBQYDK2VwBCIEIPkucDMoZPkyltc200nNyyfJKWP7cu3Tr9gdsFB6PeqN
+-----END PRIVATE KEY-----
diff --git a/modules/eddsa/src/test/resources/public.pem b/modules/eddsa/src/test/resources/public.pem
new file mode 100644
index 0000000..d457336
--- /dev/null
+++ b/modules/eddsa/src/test/resources/public.pem
@@ -0,0 +1,3 @@
+-----BEGIN PUBLIC KEY-----
+MCowBQYDK2VwAyEAYNI09OpzbZ9GiKhZzNEbwWYISkR2ihfvWEsZx62b+bY=
+-----END PUBLIC KEY-----
diff --git a/modules/eddsa/src/test/scala/gs/crypto/v0/eddsa/Ed25519Tests.scala b/modules/eddsa/src/test/scala/gs/crypto/v0/eddsa/Ed25519Tests.scala
new file mode 100644
index 0000000..1d977bf
--- /dev/null
+++ b/modules/eddsa/src/test/scala/gs/crypto/v0/eddsa/Ed25519Tests.scala
@@ -0,0 +1,61 @@
+package gs.crypto.v0.eddsa
+
+import cats.effect.IO
+import cats.effect.unsafe.IORuntime
+import gs.crypto.v0.KeyLoader
+import gs.crypto.v0.SignatureValidity
+import java.security.PrivateKey
+import java.security.PublicKey
+import java.util.UUID
+import munit.Location
+
+class Ed25519Tests extends munit.FunSuite:
+  import Ed25519Tests.Resources
+
+  given IORuntime = IORuntime.global
+
+  def iotest(
+    name: String
+  )(
+    f: => IO[Unit]
+  )(
+    using
+    Location
+  ): Unit =
+    test(name)(f.unsafeRunSync())
+
+  val keyLoader = KeyLoader.resourceLoader[IO]()
+
+  iotest(
+    "should sign some data and verify that signature"
+  ) {
+    val data = UUID.randomUUID().toString()
+    loadKeysOrFail().flatMap { case (publicKey, privateKey) =>
+      val signer   = new Ed25519Signer[IO](privateKey)
+      val verifier = new Ed25519Verifier[IO](publicKey)
+
+      for
+        signature <- signer.sign(data)
+        validity  <- verifier.verify(signature, data.getBytes())
+      yield assertEquals(validity, SignatureValidity.Valid)
+    }
+  }
+
+  private def loadKeysOrFail(): IO[(PublicKey, PrivateKey)] =
+    keyLoader.loadPublicKey(Resources.PublicKey, Ed25519.Algorithm).flatMap {
+      case Left(_) => fail("Failed to load public key.")
+      case Right(pub) =>
+        keyLoader.loadPrivateKey(Resources.PrivateKey, Ed25519.Algorithm).map {
+          case Left(_)     => fail("Failed to load private key.")
+          case Right(priv) => (pub, priv)
+        }
+    }
+
+object Ed25519Tests:
+
+  object Resources:
+    val PublicKey: String  = "public.pem"
+    val PrivateKey: String = "private.pem"
+  end Resources
+
+end Ed25519Tests
diff --git a/project/build.properties b/project/build.properties
index 4d6c567..c9aaa51 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.12.2
+sbt.version=1.12.4