diff --git a/LICENSE b/LICENSE
index 3b4e6e9..d9228fd 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,7 @@
 BSD 3-Clause License
 
 Copyright (c) 2021, James Bowes
+Copyright (c) 2023, Alexander Taraymovich, OffBlocks
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
diff --git a/README.md b/README.md
index f2b9c29..323bd88 100644
--- a/README.md
+++ b/README.md
@@ -33,6 +33,37 @@ and the request path.
 
 ## Usage
 
+### Standalone Signing and Verification
+
+To sign a request, first instantiate a `Signer` using your preferred key and signing algorithm:
+
+```go
+// Create a signer
+signer := httpsig.NewSigner(httpsig.WithSignEcdsaP256Sha256("key1", privKey))
+
+// Create a request
+req, _ := http.NewRequest("GET", "https://some-url.com", nil)
+
+// Sign the request
+header, _ := signer.Sign(httpsig.MessageFromRequest(req))
+
+// Add the signature to the request
+req.Header = header
+```
+
+To verify a response, instantiate a `Verifier` using your preferred key and signing algorithm:
+
+```go
+// Receive a response from server
+resp, _ := client.Post("https://some-url.com", "application/json", &buf)
+
+// Create a verifier
+verifier := httpsig.NewVerifier(httpsig.WithVerifyEcdsaP256Sha256("key1", pubKey))
+
+// Verify the response
+err := verifier.Verify(httpsig.MessageFromResponse(resp))
+```
+
 ### Signing HTTP Requests in Clients
 
 To sign HTTP requests from a client, wrap an `http.Client`'s transport with
diff --git a/base.go b/base.go
index d6e1d97..d922106 100644
--- a/base.go
+++ b/base.go
@@ -1,3 +1,34 @@
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 package httpsig
 
 import (
@@ -59,7 +90,7 @@ func createSigningParameters(config *SignConfig) *httpsfv.Params {
 	}
 
 	if slices.Contains(params, ParamKeyID) {
-		// attempt to obtain an overriden key id, otherwise use the one supplied by the key
+		// attempt to obtain an overridden key id, otherwise use the one supplied by the key
 		var keyID *string
 		if config.ParamValues != nil && config.ParamValues.KeyID != nil {
 			keyID = config.ParamValues.KeyID
@@ -71,7 +102,7 @@ func createSigningParameters(config *SignConfig) *httpsfv.Params {
 	}
 
 	if slices.Contains(params, ParamAlg) {
-		// attempt to obtain an overriden algorithm, otherwise use the one supplied by the key
+		// attempt to obtain an overridden algorithm, otherwise use the one supplied by the key
 		var alg *Algorithm
 		if config.ParamValues != nil && config.ParamValues.Alg != nil {
 			alg = config.ParamValues.Alg
diff --git a/canonicalise.go b/canonicalise.go
index 1b3a671..ea4caca 100644
--- a/canonicalise.go
+++ b/canonicalise.go
@@ -1,6 +1,33 @@
-// Copyright (c) 2021 James Bowes. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 package httpsig
 
diff --git a/digest.go b/digest.go
index f8d4542..5b7ac58 100644
--- a/digest.go
+++ b/digest.go
@@ -1,3 +1,34 @@
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 package httpsig
 
 import (
@@ -15,6 +46,30 @@ type DigestConfig struct {
 	Algorithms []DigestAlgorithm
 }
 
+type Digestor struct {
+	*digestor
+}
+
+// NewDigestor creates a new digestor with the given options
+func NewDigestor(opts ...digestOption) *Digestor {
+	d := digestor{}
+
+	for _, o := range opts {
+		o.configureDigest(&d)
+	}
+
+	if len(d.config.Algorithms) == 0 {
+		d.config.Algorithms = []DigestAlgorithm{DigestAlgorithmSha256}
+	}
+
+	return &Digestor{&d}
+}
+
+// Digest creates a digest header for the given body
+func (d *Digestor) Digest(body []byte) (http.Header, error) {
+	return d.digestor.Digest(body)
+}
+
 type digestor struct {
 	config DigestConfig
 }
diff --git a/digest_test.go b/digest_test.go
index a971a82..9d08b93 100644
--- a/digest_test.go
+++ b/digest_test.go
@@ -1,3 +1,34 @@
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 package httpsig
 
 import (
diff --git a/doc.go b/doc.go
index 1fa2691..c8e3a1a 100644
--- a/doc.go
+++ b/doc.go
@@ -1,6 +1,33 @@
-// Copyright (c) 2021 James Bowes. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 /*
 Package httpsig signs and verifies HTTP requests (with body digests) according
diff --git a/example_test.go b/example_test.go
index 3092cf6..9d95b55 100644
--- a/example_test.go
+++ b/example_test.go
@@ -1,6 +1,33 @@
-// Copyright (c) 2021 James Bowes. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 package httpsig_test
 
diff --git a/httpsig.go b/httpsig.go
index 38f0764..aa26869 100644
--- a/httpsig.go
+++ b/httpsig.go
@@ -1,13 +1,35 @@
-// Copyright (c) 2021 James Bowes. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// BSD 3-Clause License
 
-package httpsig
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
 
-import (
-	"net/http"
-	"time"
-)
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package httpsig
 
 const (
 	SignatureHeader      = "Signature"
@@ -15,19 +37,13 @@ const (
 	ContentDigestHeader  = "Content-Digest"
 )
 
-type Param string
-
-const (
-	ParamKeyID   Param = "keyid"
-	ParamAlg     Param = "alg"
-	ParamCreated Param = "created"
-	ParamExpires Param = "expires"
-	ParamNonce   Param = "nonce"
-	ParamTag     Param = "tag"
-)
-
-var defaultParams = []Param{ParamKeyID, ParamAlg, ParamCreated}
-
+// Algorithm is the signature algorithm to use. Available algorithms are:
+// - RSASSA-PKCS1-v1_5 using SHA-256 (rsa-v1_5-sha256)
+// - RSASSA-PSS using SHA-512 (rsa-pss-sha512)
+// - ECDSA using curve P-256 DSS and SHA-256 (ecdsa-p256-sha256)
+// - ECDSA using curve P-384 DSS and SHA-384 (ecdsa-p384-sha384)
+// - EdDSA using curve edwards25519 (ed25519)
+// - HMAC using SHA-256 (hmac-sha256)
 type Algorithm string
 
 const (
@@ -39,112 +55,12 @@ const (
 	AlgorithmHmacSha256        Algorithm = "hmac-sha256"
 )
 
+// DigestAlgorithm is the digest algorithm to use. Available algorithms are:
+// - SHA-256 (sha-256)
+// - SHA-512 (sha-512)
 type DigestAlgorithm string
 
 const (
 	DigestAlgorithmSha256 DigestAlgorithm = "sha-256"
 	DigestAlgorithmSha512 DigestAlgorithm = "sha-512"
 )
-
-type SigningKey interface {
-	Sign(data []byte) ([]byte, error)
-	GetKeyID() string
-	GetAlgorithm() Algorithm
-}
-
-// The signature parameters to include in signing
-type SignatureParameters struct {
-	// The created time for the signature. `nil` indicates not to populate the `created` time
-	// default: time.Now()
-	Created *time.Time
-
-	// The time the signature should be deemed to have expired
-	// default: time.Now() + 5 mins
-	Expires *time.Time
-
-	// A nonce for the request
-	Nonce *string
-
-	// The algorithm the signature is signed with (overrides the alg provided by the signing key)
-	Alg *Algorithm
-
-	// The key id the signature is signed with (overrides the keyid provided by the signing key)
-	KeyID *string
-
-	// A tag parameter for the signature
-	Tag *string
-}
-
-type Signer struct {
-	*signer
-}
-
-func NewSigner(opts ...signOption) *Signer {
-	s := signer{}
-
-	for _, o := range opts {
-		o.configureSign(&s)
-	}
-
-	if len(s.config.Params) == 0 {
-		s.config.Params = defaultParams[:]
-	}
-
-	return &Signer{&s}
-}
-
-func (s *Signer) Sign(m *Message) (http.Header, error) {
-	return s.signer.Sign(m)
-}
-
-type VerifyingKey interface {
-	Verify(data []byte, signature []byte) error
-	GetKeyID() string
-	GetAlgorithm() Algorithm
-}
-
-type VerifyingKeyResolver interface {
-	Resolve(keyID string) (VerifyingKey, error)
-}
-
-type Verifier struct {
-	*verifier
-}
-
-func NewVerifier(opts ...verifyOption) *Verifier {
-	v := verifier{}
-
-	v.config.Keys = make(map[string]VerifyingKey)
-
-	for _, o := range opts {
-		o.configureVerify(&v)
-	}
-
-	return &Verifier{&v}
-}
-
-func (v *Verifier) Verify(m *Message) error {
-	err := v.verifier.Verify(m)
-	if err != nil {
-		return err
-	}
-	return nil
-}
-
-type Digestor struct {
-	*digestor
-}
-
-func NewDigestor(opts ...digestOption) *Digestor {
-	d := digestor{}
-
-	for _, o := range opts {
-		o.configureDigest(&d)
-	}
-
-	if len(d.config.Algorithms) == 0 {
-		d.config.Algorithms = []DigestAlgorithm{DigestAlgorithmSha256}
-	}
-
-	return &Digestor{&d}
-}
diff --git a/middleware.go b/middleware.go
index 479e161..44370a4 100644
--- a/middleware.go
+++ b/middleware.go
@@ -1,3 +1,34 @@
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 package httpsig
 
 import "net/http"
@@ -5,8 +36,8 @@ import "net/http"
 // NewVerifyMiddleware returns a configured http server middleware that can be used to wrap
 // multiple handlers for http message signature and digest verification.
 //
-// Use the `WithVerify*` option funcs to configure signature verification algorithms that map
-// to their provided key ids.
+// Use the `WithVerify*` option funcs to configure signature verification algorithms and verification
+// parameters.
 //
 // Requests with missing signatures, malformed signature headers, expired signatures, or
 // invalid signatures are rejected with a `400` response. Only one valid signature is required
diff --git a/option.go b/option.go
index b2d1745..ad99dfd 100644
--- a/option.go
+++ b/option.go
@@ -1,3 +1,34 @@
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 package httpsig
 
 import (
diff --git a/signer.go b/signer.go
index dd6e832..1cd76f6 100644
--- a/signer.go
+++ b/signer.go
@@ -1,6 +1,33 @@
-// Copyright (c) 2021 James Bowes. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 package httpsig
 
@@ -17,10 +44,25 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"time"
 
 	"github.com/dunglas/httpsfv"
 )
 
+type Param string
+
+const (
+	ParamKeyID   Param = "keyid"
+	ParamAlg     Param = "alg"
+	ParamCreated Param = "created"
+	ParamExpires Param = "expires"
+	ParamNonce   Param = "nonce"
+	ParamTag     Param = "tag"
+)
+
+var defaultParams = []Param{ParamKeyID, ParamAlg, ParamCreated}
+
+// SignConfig is the configuration for a signer
 type SignConfig struct {
 	// The key to use for signing
 	Key SigningKey
@@ -43,6 +85,62 @@ type SignConfig struct {
 	ParamValues *SignatureParameters
 }
 
+// The key to use for signing
+type SigningKey interface {
+	Sign(data []byte) ([]byte, error)
+	GetKeyID() string
+	GetAlgorithm() Algorithm
+}
+
+// The signature parameters to include in signing
+type SignatureParameters struct {
+	// The created time for the signature. `nil` indicates not to populate the `created` time
+	// default: time.Now()
+	Created *time.Time
+
+	// The time the signature should be deemed to have expired
+	// default: time.Now() + 5 mins
+	Expires *time.Time
+
+	// A nonce for the request
+	Nonce *string
+
+	// The algorithm the signature is signed with (overrides the alg provided by the signing key)
+	Alg *Algorithm
+
+	// The key id the signature is signed with (overrides the keyid provided by the signing key)
+	KeyID *string
+
+	// A tag parameter for the signature
+	Tag *string
+}
+
+type Signer struct {
+	*signer
+}
+
+// NewSigner creates a new signer with the given options
+//
+// Use the `WithSign*` option funcs to configure signing algorithms and parameters.
+func NewSigner(opts ...signOption) *Signer {
+	s := signer{}
+
+	for _, o := range opts {
+		o.configureSign(&s)
+	}
+
+	if len(s.config.Params) == 0 {
+		s.config.Params = defaultParams[:]
+	}
+
+	return &Signer{&s}
+}
+
+// Sign signs the given message and returns updated request headers
+func (s *Signer) Sign(m *Message) (http.Header, error) {
+	return s.signer.Sign(m)
+}
+
 type signer struct {
 	config SignConfig
 }
diff --git a/spec_test.go b/spec_test.go
index 7e72962..666b168 100644
--- a/spec_test.go
+++ b/spec_test.go
@@ -1,6 +1,33 @@
-// Copyright (c) 2021 James Bowes. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 package httpsig
 
diff --git a/transport.go b/transport.go
index 380db79..c0c3880 100644
--- a/transport.go
+++ b/transport.go
@@ -1,3 +1,34 @@
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 package httpsig
 
 import "net/http"
diff --git a/verifier.go b/verifier.go
index 13a638e..c6a737b 100644
--- a/verifier.go
+++ b/verifier.go
@@ -1,6 +1,33 @@
-// Copyright (c) 2021 James Bowes. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// BSD 3-Clause License
+
+// Copyright (c) 2021, James Bowes
+// Copyright (c) 2023, Alexander Taraymovich, OffBlocks
+// All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 package httpsig
 
@@ -20,6 +47,7 @@ import (
 	"github.com/dunglas/httpsfv"
 )
 
+// VerifyConfig is the configuration for a verifier
 type VerifyConfig struct {
 	// The keys to use for signing
 	Keys map[string]VerifyingKey
@@ -53,6 +81,43 @@ type VerifyConfig struct {
 	All bool
 }
 
+// VerifyingKey is the key to use for verifying a signature
+type VerifyingKey interface {
+	Verify(data []byte, signature []byte) error
+	GetKeyID() string
+	GetAlgorithm() Algorithm
+}
+
+// VerifyingKeyResolver is used to resolve a key id to a verifying key
+type VerifyingKeyResolver interface {
+	Resolve(keyID string) (VerifyingKey, error)
+}
+
+type Verifier struct {
+	*verifier
+}
+
+// NewVerifier creates a new verifier with the given options
+//
+// Use the `WithVerify*` option funcs to configure signature verification algorithms and verification
+// parameters.
+func NewVerifier(opts ...verifyOption) *Verifier {
+	v := verifier{}
+
+	v.config.Keys = make(map[string]VerifyingKey)
+
+	for _, o := range opts {
+		o.configureVerify(&v)
+	}
+
+	return &Verifier{&v}
+}
+
+// Verify verifies the given message
+func (v *Verifier) Verify(m *Message) error {
+	return v.verifier.Verify(m)
+}
+
 type clock interface {
 	Now() time.Time
 }