diff --git a/relay_rpc/Cargo.toml b/relay_rpc/Cargo.toml
index 976281f..d3b03c3 100644
--- a/relay_rpc/Cargo.toml
+++ b/relay_rpc/Cargo.toml
@@ -17,3 +17,6 @@ chrono = { version = "0.4", default-features = false, features = ["std", "clock"
 regex = "1.7"
 once_cell = "1.16"
 jsonwebtoken = "8.1"
+k256 = "0.13.0"
+sha3 = "0.10.6"
+hex = "0.4.3"
\ No newline at end of file
diff --git a/relay_rpc/src/auth.rs b/relay_rpc/src/auth.rs
index fde229c..8d02601 100644
--- a/relay_rpc/src/auth.rs
+++ b/relay_rpc/src/auth.rs
@@ -1,6 +1,9 @@
 #[cfg(test)]
 mod tests;
 
+pub mod cacao;
+pub mod did;
+
 use {
     crate::domain::{AuthSubject, ClientId, ClientIdDecodingError, DecodedClientId},
     chrono::{DateTime, Utc},
diff --git a/relay_rpc/src/auth/cacao/header.rs b/relay_rpc/src/auth/cacao/header.rs
new file mode 100644
index 0000000..fbc1c76
--- /dev/null
+++ b/relay_rpc/src/auth/cacao/header.rs
@@ -0,0 +1,18 @@
+use {
+    super::CacaoError,
+    serde::{Deserialize, Serialize},
+};
+
+#[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize, Hash)]
+pub struct Header {
+    pub t: String,
+}
+
+impl Header {
+    pub fn is_valid(&self) -> Result<(), CacaoError> {
+        match self.t.as_str() {
+            "eip4361" => Ok(()),
+            _ => Err(CacaoError::Header),
+        }
+    }
+}
diff --git a/relay_rpc/src/auth/cacao/mod.rs b/relay_rpc/src/auth/cacao/mod.rs
new file mode 100644
index 0000000..4eb1942
--- /dev/null
+++ b/relay_rpc/src/auth/cacao/mod.rs
@@ -0,0 +1,133 @@
+use {
+    self::{header::Header, payload::Payload, signature::Signature},
+    core::fmt::Debug,
+    serde::{Deserialize, Serialize},
+    std::fmt::{Display, Write as _},
+    thiserror::Error as ThisError,
+};
+
+pub mod header;
+pub mod payload;
+pub mod signature;
+
+/// Errors that can occur during JWT verification
+#[derive(Debug, ThisError)]
+pub enum CacaoError {
+    #[error("Invalid header")]
+    Header,
+
+    #[error("Invalid or missing identity key in payload resources")]
+    PayloadIdentityKey,
+
+    #[error("Invalid payload resources")]
+    PayloadResources,
+
+    #[error("Unsupported signature type")]
+    UnsupportedSignature,
+
+    #[error("Unable to verify")]
+    Verification,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Version {
+    V1 = 1,
+}
+
+impl<'de> Deserialize<'de> for Version {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let version = String::deserialize(deserializer)?;
+        match version.as_str() {
+            "1" => Ok(Version::V1),
+            _ => Err(serde::de::Error::custom("Invalid version")),
+        }
+    }
+}
+
+impl Serialize for Version {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.serialize_str(&format!("{}", *self as u8))
+    }
+}
+
+impl Display for Version {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", *self as u8)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize, Hash)]
+pub struct Cacao {
+    pub h: Header,
+    pub p: Payload,
+    pub s: Signature,
+}
+
+impl Cacao {
+    const ETHEREUM: &'static str = "Ethereum";
+
+    pub fn verify(&self) -> Result<bool, CacaoError> {
+        self.p.is_valid()?;
+        self.h.is_valid()?;
+        self.s.verify(self)
+    }
+
+    pub fn siwe_message(&self) -> Result<String, CacaoError> {
+        self.caip122_message(Self::ETHEREUM)
+    }
+
+    pub fn caip122_message(&self, chain_name: &str) -> Result<String, CacaoError> {
+        let mut message = format!(
+            "{} wants you to sign in with your {} account:\n{}\n",
+            self.p.domain,
+            chain_name,
+            self.p.address()?
+        );
+
+        if let Some(statement) = &self.p.statement {
+            let _ = write!(message, "\n{}\n", statement);
+        }
+
+        let _ = write!(
+            message,
+            "\nURI: {}\nVersion: {}\nChain ID: {}\nNonce: {}\nIssued At: {}",
+            self.p.aud,
+            self.p.version,
+            self.p.chain_id()?,
+            self.p.nonce,
+            self.p.iat
+        );
+
+        if let Some(exp) = &self.p.exp {
+            let _ = write!(message, "\nExpiration Time: {}", exp);
+        }
+
+        if let Some(nbf) = &self.p.nbf {
+            let _ = write!(message, "\nNot Before: {}", nbf);
+        }
+
+        if let Some(request_id) = &self.p.request_id {
+            let _ = write!(message, "\nRequest ID: {}", request_id);
+        }
+
+        if let Some(resources) = &self.p.resources {
+            if !resources.is_empty() {
+                let _ = write!(message, "\nResources:");
+                resources.iter().for_each(|resource| {
+                    let _ = write!(message, "\n- {}", resource);
+                });
+            }
+        }
+
+        Ok(message)
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/relay_rpc/src/auth/cacao/payload.rs b/relay_rpc/src/auth/cacao/payload.rs
new file mode 100644
index 0000000..ab8bf3c
--- /dev/null
+++ b/relay_rpc/src/auth/cacao/payload.rs
@@ -0,0 +1,87 @@
+use {
+    super::{CacaoError, Version},
+    crate::auth::did::{extract_did_data, DID_METHOD_KEY},
+    serde::{Deserialize, Serialize},
+};
+
+#[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize, Hash)]
+pub struct Payload {
+    pub domain: String,
+    pub iss: String,
+    pub statement: Option<String>,
+    pub aud: String,
+    pub version: Version,
+    pub nonce: String,
+    pub iat: String,
+    pub exp: Option<String>,
+    pub nbf: Option<String>,
+    pub request_id: Option<String>,
+    pub resources: Option<Vec<String>>,
+}
+
+impl Payload {
+    const ISS_DELIMITER: &'static str = ":";
+    const ISS_POSITION_OF_ADDRESS: usize = 4;
+    const ISS_POSITION_OF_NAMESPACE: usize = 2;
+    const ISS_POSITION_OF_REFERENCE: usize = 3;
+
+    /// TODO: write valdation
+    pub fn is_valid(&self) -> Result<bool, CacaoError> {
+        Ok(true)
+    }
+
+    pub fn address(&self) -> Result<String, CacaoError> {
+        self.iss
+            .split(Self::ISS_DELIMITER)
+            .nth(Self::ISS_POSITION_OF_ADDRESS)
+            .ok_or(CacaoError::PayloadResources)
+            .map(|s| s.to_string())
+    }
+
+    pub fn namespace(&self) -> Result<String, CacaoError> {
+        self.iss
+            .split(Self::ISS_DELIMITER)
+            .nth(Self::ISS_POSITION_OF_NAMESPACE)
+            .ok_or(CacaoError::PayloadResources)
+            .map(|s| s.to_string())
+    }
+
+    pub fn chain_id_reference(&self) -> Result<String, CacaoError> {
+        Ok(format!(
+            "{}{}{}",
+            self.namespace()?,
+            Self::ISS_DELIMITER,
+            self.chain_id()?
+        ))
+    }
+
+    pub fn chain_id(&self) -> Result<String, CacaoError> {
+        self.iss
+            .split(Self::ISS_DELIMITER)
+            .nth(Self::ISS_POSITION_OF_REFERENCE)
+            .ok_or(CacaoError::PayloadResources)
+            .map(|s| s.to_string())
+    }
+
+    pub fn caip_10_address(&self) -> Result<String, CacaoError> {
+        Ok(format!(
+            "{}{}{}",
+            self.chain_id_reference()?,
+            Self::ISS_DELIMITER,
+            self.address()?
+        )
+        .to_lowercase())
+    }
+
+    pub fn identity_key(&self) -> Result<String, CacaoError> {
+        let resources = self
+            .resources
+            .as_ref()
+            .ok_or(CacaoError::PayloadResources)?;
+        let did_key = resources.first().ok_or(CacaoError::PayloadIdentityKey)?;
+
+        extract_did_data(did_key, DID_METHOD_KEY)
+            .map(|data| data.to_string())
+            .map_err(|_| CacaoError::PayloadIdentityKey)
+    }
+}
diff --git a/relay_rpc/src/auth/cacao/signature.rs b/relay_rpc/src/auth/cacao/signature.rs
new file mode 100644
index 0000000..49e86a4
--- /dev/null
+++ b/relay_rpc/src/auth/cacao/signature.rs
@@ -0,0 +1,75 @@
+use {
+    super::{Cacao, CacaoError},
+    serde::{Deserialize, Serialize},
+};
+
+#[derive(Clone, Debug, PartialEq, Eq, Deserialize, Serialize, Hash)]
+pub struct Signature {
+    pub t: String,
+    pub s: String,
+}
+
+impl Signature {
+    pub fn verify(&self, cacao: &Cacao) -> Result<bool, CacaoError> {
+        match self.t.as_str() {
+            "eip191" => Eip191.verify(&cacao.s.s, &cacao.p.address()?, &cacao.siwe_message()?),
+            // "eip1271" => Eip1271.verify(), TODO: How to accces our RPC?
+            _ => Err(CacaoError::UnsupportedSignature),
+        }
+    }
+}
+
+pub struct Eip191;
+
+impl Eip191 {
+    pub fn eip191_bytes(&self, message: &str) -> Vec<u8> {
+        format!(
+            "\u{0019}Ethereum Signed Message:\n{}{}",
+            message.as_bytes().len(),
+            message
+        )
+        .into()
+    }
+
+    fn verify(&self, signature: &str, address: &str, message: &str) -> Result<bool, CacaoError> {
+        use {
+            k256::ecdsa::{RecoveryId, Signature as Sig, VerifyingKey},
+            sha3::{Digest, Keccak256},
+        };
+
+        let signature_bytes = hex::decode(guarantee_no_hex_prefix(signature))
+            .map_err(|_| CacaoError::Verification)?;
+
+        let sig = Sig::try_from(&signature_bytes[..64]).map_err(|_| CacaoError::Verification)?;
+        let recovery_id = RecoveryId::try_from(&signature_bytes[64] % 27)
+            .map_err(|_| CacaoError::Verification)?;
+
+        let recovered_key = VerifyingKey::recover_from_digest(
+            Keccak256::new_with_prefix(&self.eip191_bytes(message)),
+            &sig,
+            recovery_id,
+        )
+        .map_err(|_| CacaoError::Verification)?;
+
+        let add = &Keccak256::default()
+            .chain_update(&recovered_key.to_encoded_point(false).as_bytes()[1..])
+            .finalize()[12..];
+
+        let address_encoded = hex::encode(add);
+
+        if address_encoded.to_lowercase() != guarantee_no_hex_prefix(address).to_lowercase() {
+            Err(CacaoError::Verification)
+        } else {
+            Ok(true)
+        }
+    }
+}
+
+/// Remove the 0x prefix from a hex string
+fn guarantee_no_hex_prefix(s: &str) -> &str {
+    if let Some(stripped) = s.strip_prefix("0x") {
+        stripped
+    } else {
+        s
+    }
+}
diff --git a/relay_rpc/src/auth/cacao/tests.rs b/relay_rpc/src/auth/cacao/tests.rs
new file mode 100644
index 0000000..4e3a206
--- /dev/null
+++ b/relay_rpc/src/auth/cacao/tests.rs
@@ -0,0 +1,46 @@
+use crate::auth::cacao::Cacao;
+
+/// Test that we can verify a Cacao
+#[test]
+fn cacao_verify_success() {
+    let cacao_serialized = r#"{
+      "h": {
+        "t": "eip4361"
+      },
+      "p": {
+        "iss": "did:pkh:eip155:1:0xf457f233ab23f863cabc383ebb37b29d8929a17a",
+        "domain": "http://10.0.2.2:8080",
+        "aud": "http://10.0.2.2:8080",
+        "version": "1",
+        "nonce": "[B@c3772c7",
+        "iat": "2023-01-17T12:15:05+01:00",
+        "resources": [
+          "did:key:z6MkkG9nM8ksS37sq5mgeoCn5kihLkWANcm9pza5WTkq3tWZ"
+        ]
+      },
+      "s": {
+        "t": "eip191",
+        "s": "0x1b39982707c70c95f4676e7386052a07b47ecc073b3e9cf47b64b579687d3f68181d48fa9e926ad591ba6954f1a70c597d0772a800bed5fa906384fcd83bcf4f1b"
+      }
+    } "#;
+    let cacao: Cacao = serde_json::from_str(cacao_serialized).unwrap();
+    let result = cacao.verify();
+    assert!(result.is_ok());
+    assert!(result.map_err(|_| false).unwrap());
+
+    let identity_key = cacao.p.identity_key();
+    assert!(identity_key.is_ok());
+}
+
+/// Test that we can verify a Cacao with uppercase address
+#[test]
+fn cacao_without_lowercase_address_verify_success() {
+    let cacao_serialized = r#"{"h":{"t":"eip4361"},"p":{"iss":"did:pkh:eip155:1:0xbD4D1935165012e7D29919dB8717A5e670a1a5b1","domain":"https://staging.keys.walletconnect.com","aud":"https://staging.keys.walletconnect.com","version":"1","nonce":"07487c09be5535dcbc341d8e35e5c9b4d3539a802089c42c5b1172dd9ed63c64","iat":"2023-01-25T15:08:36.846Z","statement":"Test","resources":["did:key:451cf9b97c64fcca05fbb0d4c40b886c94133653df5a2b6bd97bd29a0bbcdb37"]},"s":{"t":"eip191","s":"0x8496ad1dd1ddd5cb78ac26b62a6bd1c6cfff703ea3b11a9da29cfca112357ace75cac8ee28d114f9e166a6935ee9ed83151819a9e0ee738a0547116b1d978e351b"}}"#;
+    let cacao: Cacao = serde_json::from_str(cacao_serialized).unwrap();
+    let result = cacao.verify();
+    assert!(result.is_ok());
+    assert!(result.map_err(|_| false).unwrap());
+
+    let identity_key = cacao.p.identity_key();
+    assert!(identity_key.is_ok());
+}
diff --git a/relay_rpc/src/auth/did.rs b/relay_rpc/src/auth/did.rs
new file mode 100644
index 0000000..3703f99
--- /dev/null
+++ b/relay_rpc/src/auth/did.rs
@@ -0,0 +1,31 @@
+pub const DID_DELIMITER: &str = ":";
+pub const DID_PREFIX: &str = "did";
+pub const DID_METHOD_KEY: &str = "key";
+pub const DID_METHOD_PKH: &str = "pkh";
+
+use thiserror::Error as ThisError;
+
+#[derive(Debug, ThisError)]
+pub enum DidError {
+    #[error("Invalid issuer DID prefix")]
+    Prefix,
+
+    #[error("Invalid issuer DID method")]
+    Method,
+
+    #[error("Invalid issuer format")]
+    Format,
+}
+
+pub fn extract_did_data<'a>(did: &'a str, method: &'a str) -> Result<&'a str, DidError> {
+    let data = did
+        .strip_prefix(DID_PREFIX)
+        .ok_or(DidError::Prefix)?
+        .strip_prefix(DID_DELIMITER)
+        .ok_or(DidError::Format)?
+        .strip_prefix(method)
+        .ok_or(DidError::Method)?
+        .strip_prefix(DID_DELIMITER)
+        .ok_or(DidError::Format)?;
+    Ok(data)
+}