diff --git a/Cargo.lock b/Cargo.lock
index 3199dc0..d8550ab 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,9 +14,9 @@ dependencies = [
 
 [[package]]
 name = "aes"
-version = "0.9.1"
+version = "0.9.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f1fc76eaeac4c9164506c466d4ffdd8ec9d0c5bf57ee97177c4d8eceb3a0e138"
+checksum = "f8eb277bec05f56a0e0591f155a484cbd0f4f07ff2905051a48c72f004f7ed58"
 dependencies = [
  "cipher",
  "cpubits",
@@ -66,9 +66,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.2.67"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e17dd265a7d0f31ef544e1b20e03add05d3b45b491b633b10d67145d2acc1a38"
+checksum = "5add81bb678e6cb321aff7fa0dc7689ad82b112dbc032cea19f91d6b8e3582b9"
 dependencies = [
  "find-msvc-tools",
  "shlex",
@@ -220,7 +220,7 @@ checksum = "f46882e17999c6cc590af592290432be3bce0428cb0d5f8b6715e4dc7b383eb3"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -393,9 +393,9 @@ dependencies = [
 
 [[package]]
 name = "hybrid-array"
-version = "0.4.13"
+version = "0.4.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "818356c5132c1fede50f837ca96afbe78ff42413047f4abb886217845e1b6c8c"
+checksum = "707114b52a152fa7bdb290cd7cd5912d9467273b6d74e21b8d81aca1f8533f6b"
 dependencies = [
  "subtle",
  "typenum",
@@ -413,9 +413,9 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.186"
+version = "0.2.189"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68ab91017fe16c622486840e4c83c9a37afeff978bd239b5293d61ece587de66"
+checksum = "3eaf3ede3fee6db1a4c2ee091bf8a8b4dccdc6d17f656fb07896ee72867612f2"
 
 [[package]]
 name = "log"
@@ -465,6 +465,20 @@ dependencies = [
  "sha2",
 ]
 
+[[package]]
+name = "p521"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ad64cc32c2dc466317c12ee5853e61f159f9eab1fe7efade0395dc2e7b43449"
+dependencies = [
+ "base16ct",
+ "ecdsa",
+ "elliptic-curve",
+ "primefield",
+ "primeorder",
+ "sha2",
+]
+
 [[package]]
 name = "paste"
 version = "1.0.15"
@@ -548,18 +562,18 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.106"
+version = "1.0.107"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8fd00f0bb2e90d81d1044c2b32617f68fcb9fa3bb7640c23e9c748e53fb30934"
+checksum = "985e7ec9bb745e6ce6535b544d84d6cd6f7ad8bd711c398938ae983b91a766d9"
 dependencies = [
  "unicode-ident",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.46"
+version = "1.0.47"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dfbc457d0c7a0759a614551b11a6409e5951f6c7537be1f1b7682b9ae9230368"
+checksum = "1fbf4db142a473a8d80c26bbf18454ed458bf8d26c8219c331daecfdbd079001"
 dependencies = [
  "proc-macro2",
 ]
@@ -630,9 +644,9 @@ dependencies = [
 
 [[package]]
 name = "rustls"
-version = "0.23.42"
+version = "0.23.43"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3c54fcab019b409d04215d3a17cb438fd7fbf192ee61461f20f4fe18704bc138"
+checksum = "0283386ce02abc0151e1761d08802dfe86c173b0b494af5cbc086574e453da06"
 dependencies = [
  "log",
  "once_cell",
@@ -644,9 +658,9 @@ dependencies = [
 
 [[package]]
 name = "rustls-pki-types"
-version = "1.15.0"
+version = "1.15.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "764899a24af3980067ee14bc143654f297b22eaebfe3c7b6b211920a5a59b046"
+checksum = "2f4925028c7eb5d1fcdaf196971378ed9d2c1c4efc7dc5d011256f76c99c0a96"
 dependencies = [
  "zeroize",
 ]
@@ -667,6 +681,7 @@ dependencies = [
  "hmac",
  "p256",
  "p384",
+ "p521",
  "paste",
  "pkcs8",
  "rsa",
@@ -711,31 +726,31 @@ checksum = "8a7852d02fc848982e0c167ef163aaff9cd91dc640ba85e263cb1ce46fae51cd"
 
 [[package]]
 name = "serde"
-version = "1.0.228"
+version = "1.0.229"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9a8e94ea7f378bd32cbbd37198a4a91436180c5bb472411e48b5ec2e2124ae9e"
+checksum = "4148590afebada386688f18773da617792bf2ef03ffc1e4cbd2b1d45b023e0ba"
 dependencies = [
  "serde_core",
 ]
 
 [[package]]
 name = "serde_core"
-version = "1.0.228"
+version = "1.0.229"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "41d385c7d4ca58e59fc732af25c3983b67ac852c1a25000afe1175de458b67ad"
+checksum = "67dca2c9c51e58a4791a4b1ed58308b39c64224d349a935ab5039aa360942a48"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.228"
+version = "1.0.229"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d540f220d3187173da220f885ab66608367b6574e925011a9353e4badda91d79"
+checksum = "e7a5d71263a5a7d47b41f6b3f06ba276f10cc18b0931f1799f710578e2309348"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 3.0.3",
 ]
 
 [[package]]
@@ -802,6 +817,17 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "syn"
+version = "3.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "53e9bae58849f64dfa4f5d5ae372c8341f7305f82a3868709269343628b659a3"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "typenum"
 version = "1.20.1"
diff --git a/Cargo.toml b/Cargo.toml
index e8e5de0..3cead0e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -30,6 +30,7 @@ getrandom = { version = "0.4", default-features = false, features = ["sys_rng"]
 hmac = { version = "0.13", default-features = false }
 p256 = { version = "0.14", default-features = false, features = ["pem", "ecdsa", "ecdh"] }
 p384 = { version = "0.14", default-features = false, features = ["pem", "ecdsa", "ecdh"] }
+p521 = { version = "0.14", default-features = false, features = ["pem", "ecdsa", "ecdh"] }
 paste = { version = "1", default-features = false }
 pkcs8 = { version = "0.11", default-features = false }
 pki-types = { package = "rustls-pki-types", version = "1", default-features = false }
diff --git a/src/kx.rs b/src/kx.rs
index 3f8a4dd..3fef28c 100644
--- a/src/kx.rs
+++ b/src/kx.rs
@@ -108,5 +108,6 @@ macro_rules! impl_kx {
 
 impl_kx! {SecP256R1, rustls::NamedGroup::secp256r1, p256::ecdh::EphemeralSecret, p256::PublicKey}
 impl_kx! {SecP384R1, rustls::NamedGroup::secp384r1, p384::ecdh::EphemeralSecret, p384::PublicKey}
+impl_kx! {SecP521R1, rustls::NamedGroup::secp521r1, p521::ecdh::EphemeralSecret, p521::PublicKey}
 
-pub const ALL_KX_GROUPS: &[&dyn SupportedKxGroup] = &[&X25519, &SecP256R1, &SecP384R1];
+pub const ALL_KX_GROUPS: &[&dyn SupportedKxGroup] = &[&X25519, &SecP256R1, &SecP384R1, &SecP521R1];
diff --git a/src/sign.rs b/src/sign.rs
index cf30cc5..c1d2edc 100644
--- a/src/sign.rs
+++ b/src/sign.rs
@@ -2,7 +2,7 @@
 use alloc::{sync::Arc, vec::Vec};
 use core::marker::PhantomData;
 
-use self::ecdsa::{EcdsaSigningKeyP256, EcdsaSigningKeyP384};
+use self::ecdsa::{EcdsaSigningKeyP256, EcdsaSigningKeyP384, EcdsaSigningKeyP521};
 use self::eddsa::Ed25519SigningKey;
 use self::rsa::RsaSigningKey;
 
@@ -89,7 +89,8 @@ pub fn any_supported_type(der: &PrivateKeyDer<'_>) -> Result<Arc<dyn SigningKey>
 pub fn any_ecdsa_type(der: &PrivateKeyDer<'_>) -> Result<Arc<dyn SigningKey>, rustls::Error> {
     let p256 = |_| EcdsaSigningKeyP256::try_from(der).map(|x| Arc::new(x) as _);
     let p384 = |_| EcdsaSigningKeyP384::try_from(der).map(|x| Arc::new(x) as _);
-    p256(()).or_else(p384)
+    let p521 = |_| EcdsaSigningKeyP521::try_from(der).map(|x| Arc::new(x) as _);
+    p256(()).or_else(p384).or_else(p521)
 }
 
 /// Extract any supported EDDSA key from the given DER input.
diff --git a/src/sign/ecdsa.rs b/src/sign/ecdsa.rs
index 347bc25..6e9dfc2 100644
--- a/src/sign/ecdsa.rs
+++ b/src/sign/ecdsa.rs
@@ -69,3 +69,4 @@ macro_rules! impl_ecdsa {
 
 impl_ecdsa! {P256, SignatureScheme::ECDSA_NISTP256_SHA256, p256::ecdsa::SigningKey, p256::ecdsa::DerSignature}
 impl_ecdsa! {P384, SignatureScheme::ECDSA_NISTP384_SHA384, p384::ecdsa::SigningKey, p384::ecdsa::DerSignature}
+impl_ecdsa! {P521, SignatureScheme::ECDSA_NISTP521_SHA512, p521::ecdsa::SigningKey, p521::ecdsa::DerSignature}
diff --git a/src/verify.rs b/src/verify.rs
index 2043b64..11ab55a 100644
--- a/src/verify.rs
+++ b/src/verify.rs
@@ -1,7 +1,10 @@
 use rustls::crypto::WebPkiSupportedAlgorithms;
 use rustls::SignatureScheme;
 
-use self::ecdsa::{ECDSA_P256_SHA256, ECDSA_P256_SHA384, ECDSA_P384_SHA256, ECDSA_P384_SHA384};
+use self::ecdsa::{
+    ECDSA_P256_SHA256, ECDSA_P256_SHA384, ECDSA_P384_SHA256, ECDSA_P384_SHA384, ECDSA_P521_SHA256,
+    ECDSA_P521_SHA384, ECDSA_P521_SHA512,
+};
 use self::eddsa::ED25519;
 use self::rsa::{
     RSA_PKCS1_SHA256, RSA_PKCS1_SHA384, RSA_PKCS1_SHA512, RSA_PSS_SHA256, RSA_PSS_SHA384,
@@ -14,6 +17,9 @@ pub static ALGORITHMS: WebPkiSupportedAlgorithms = WebPkiSupportedAlgorithms {
         ECDSA_P256_SHA384,
         ECDSA_P384_SHA256,
         ECDSA_P384_SHA384,
+        ECDSA_P521_SHA256,
+        ECDSA_P521_SHA384,
+        ECDSA_P521_SHA512,
         ED25519,
         RSA_PKCS1_SHA256,
         RSA_PKCS1_SHA384,
@@ -25,12 +31,13 @@ pub static ALGORITHMS: WebPkiSupportedAlgorithms = WebPkiSupportedAlgorithms {
     mapping: &[
         (
             SignatureScheme::ECDSA_NISTP384_SHA384,
-            &[ECDSA_P384_SHA384, ECDSA_P256_SHA384],
+            &[ECDSA_P384_SHA384, ECDSA_P256_SHA384, ECDSA_P521_SHA384],
         ),
         (
             SignatureScheme::ECDSA_NISTP256_SHA256,
-            &[ECDSA_P256_SHA256, ECDSA_P384_SHA256],
+            &[ECDSA_P256_SHA256, ECDSA_P384_SHA256, ECDSA_P521_SHA256],
         ),
+        (SignatureScheme::ECDSA_NISTP521_SHA512, &[ECDSA_P521_SHA512]),
         (SignatureScheme::ED25519, &[ED25519]),
         (SignatureScheme::RSA_PKCS1_SHA256, &[RSA_PKCS1_SHA256]),
         (SignatureScheme::RSA_PKCS1_SHA384, &[RSA_PKCS1_SHA384]),
diff --git a/src/verify/ecdsa.rs b/src/verify/ecdsa.rs
index 743a6c5..3502537 100644
--- a/src/verify/ecdsa.rs
+++ b/src/verify/ecdsa.rs
@@ -51,3 +51,6 @@ impl_generic_ecdsa_verifer! {ECDSA_P256_SHA256, alg_id::ECDSA_P256, alg_id::ECDS
 impl_generic_ecdsa_verifer! {ECDSA_P256_SHA384, alg_id::ECDSA_P256, alg_id::ECDSA_SHA384, p256::ecdsa::VerifyingKey, p256::ecdsa::DerSignature, sha2::Sha384}
 impl_generic_ecdsa_verifer! {ECDSA_P384_SHA256, alg_id::ECDSA_P384, alg_id::ECDSA_SHA256, p384::ecdsa::VerifyingKey, p384::ecdsa::DerSignature, sha2::Sha256}
 impl_generic_ecdsa_verifer! {ECDSA_P384_SHA384, alg_id::ECDSA_P384, alg_id::ECDSA_SHA384, p384::ecdsa::VerifyingKey, p384::ecdsa::DerSignature, sha2::Sha384}
+impl_generic_ecdsa_verifer! {ECDSA_P521_SHA256, alg_id::ECDSA_P521, alg_id::ECDSA_SHA256, p521::ecdsa::VerifyingKey, p521::ecdsa::DerSignature, sha2::Sha256}
+impl_generic_ecdsa_verifer! {ECDSA_P521_SHA384, alg_id::ECDSA_P521, alg_id::ECDSA_SHA384, p521::ecdsa::VerifyingKey, p521::ecdsa::DerSignature, sha2::Sha384}
+impl_generic_ecdsa_verifer! {ECDSA_P521_SHA512, alg_id::ECDSA_P521, alg_id::ECDSA_SHA512, p521::ecdsa::VerifyingKey, p521::ecdsa::DerSignature, sha2::Sha512}
diff --git a/validation/local_ping_pong_openssl/src/lib.rs b/validation/local_ping_pong_openssl/src/lib.rs
index 14da95c..3aa1ae4 100644
--- a/validation/local_ping_pong_openssl/src/lib.rs
+++ b/validation/local_ping_pong_openssl/src/lib.rs
@@ -118,7 +118,6 @@ mod test {
         vs_openssl_as_client(group_list, OpenSslCipherSuites::default());
     }
     #[test]
-    #[should_panic] // no support
     fn vs_openssl_as_client_group_p521() {
         let mut group_list = OpenSslGroupsList::all_false();
         group_list.P521 = true;