diff --git a/lighthouse/state/validation/attestation_validation.rs b/lighthouse/state/validation/attestation_validation.rs
index d47d15c53..0061f7a9f 100644
--- a/lighthouse/state/validation/attestation_validation.rs
+++ b/lighthouse/state/validation/attestation_validation.rs
@@ -4,10 +4,15 @@ use super::attestation_parent_hashes::{
     ParentHashesError,
 };
 use super::db::ClientDB;
-use super::db::stores::BlockStore;
+use super::db::stores::{
+    BlockStore,
+    ValidatorStore,
+    StoreError,
+};
 use super::ssz::SszStream;
 use super::bls::{
     AggregateSignature,
+    AggregatePublicKey,
     PublicKey,
 };
 use super::utils::hash::canonical_hash;
diff --git a/lighthouse/state/validation/mod.rs b/lighthouse/state/validation/mod.rs
index 70c375754..c11d2c3c2 100644
--- a/lighthouse/state/validation/mod.rs
+++ b/lighthouse/state/validation/mod.rs
@@ -15,4 +15,5 @@ use super::transition::attestation_parent_hashes;
 use super::utils;
 
 mod attestation_validation;
+mod signatures;
 mod ssz_block;
diff --git a/lighthouse/state/validation/signatures.rs b/lighthouse/state/validation/signatures.rs
new file mode 100644
index 000000000..a2a289328
--- /dev/null
+++ b/lighthouse/state/validation/signatures.rs
@@ -0,0 +1,126 @@
+use std::collections::HashSet;
+use super::bls::{
+    AggregateSignature,
+    AggregatePublicKey,
+};
+use super::db::ClientDB;
+use super::db::stores::{
+    ValidatorStore,
+    StoreError,
+};
+use super::utils::types::Bitfield;
+
+#[derive(Debug, PartialEq)]
+pub enum SignatureVerificationError {
+    BadValidatorIndex,
+    PublicKeyCorrupt,
+    NoPublicKeyForValidator,
+    DBError(String),
+}
+
+fn verify_aggregate_signature_for_indices<T>(message: &[u8],
+                                             agg_sig: &AggregateSignature,
+                                             attestation_indices: &[usize],
+                                             bitfield: &Bitfield,
+                                             validator_store: &ValidatorStore<T>)
+    -> Result<(bool, HashSet<usize>), SignatureVerificationError>
+    where T: ClientDB + Sized
+{
+    let mut voters = HashSet::new();
+    let mut agg_pub_key = AggregatePublicKey::new();
+
+    for i in 0..attestation_indices.len() {
+        let voted = bitfield.get_bit(i);
+        if voted {
+            let validator = attestation_indices[i];
+            let pub_key = validator_store.get_public_key_by_index(i)?
+                .ok_or(SignatureVerificationError::NoPublicKeyForValidator)?;
+            agg_pub_key.add(&pub_key);
+            voters.insert(validator);
+        }
+    }
+    Ok((agg_sig.verify(&message, &agg_pub_key),
+        voters))
+}
+
+impl From<StoreError> for SignatureVerificationError {
+    fn from(error: StoreError) -> Self {
+        match error {
+            StoreError::DBError(s) =>
+                SignatureVerificationError::DBError(s),
+            StoreError::DecodeError =>
+                SignatureVerificationError::PublicKeyCorrupt,
+        }
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use super::super::bls::{
+        Keypair,
+        Signature,
+    };
+    use super::super::db::MemoryDB;
+    use std::sync::Arc;
+
+    #[test]
+    fn test_signature_verification() {
+        let message = "cats".as_bytes();
+        let signing_keypairs = vec![
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+        ];
+        let non_signing_keypairs = vec![
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+            Keypair::random(),
+        ];
+        /*
+         * Signing keypairs first, then non-signing
+         */
+        let mut all_keypairs = signing_keypairs.clone();
+        all_keypairs.append(&mut non_signing_keypairs.clone());
+
+        let attestation_indices: Vec<usize> = (0..all_keypairs.len())
+            .collect();
+        let mut bitfield = Bitfield::new();
+        for i in 0..signing_keypairs.len() {
+            bitfield.set_bit(i, true);
+        }
+
+        let db = Arc::new(MemoryDB::open());
+        let store = ValidatorStore::new(db);
+
+        for (i, keypair) in all_keypairs.iter().enumerate() {
+            store.put_public_key_by_index(i, &keypair.pk).unwrap();
+        }
+
+        let mut agg_sig = AggregateSignature::new();
+        for keypair in &signing_keypairs {
+            let sig = Signature::new(&message, &keypair.sk);
+            agg_sig.add(&sig);
+        }
+
+        let (is_valid, voters) = verify_aggregate_signature_for_indices(
+            &message,
+            &agg_sig,
+            &attestation_indices,
+            &bitfield,
+            &store).unwrap();
+
+        assert_eq!(is_valid, true);
+        (0..signing_keypairs.len())
+            .for_each(|i| assert!(voters.contains(&i)));
+        (signing_keypairs.len()..non_signing_keypairs.len())
+            .for_each(|i| assert!(!voters.contains(&i)));
+    }
+}