diff --git a/src/faest.rs b/src/faest.rs
index ff43ff5..e4eccb2 100644
--- a/src/faest.rs
+++ b/src/faest.rs
@@ -11,7 +11,7 @@ use crate::{
     universal_hashing::{VoleHasherInit, VoleHasherProcess},
     utils::Reader,
     vc::VectorCommitment,
-    vole::{volecommit, volereconstruct},
+    vole::{volecommit, volereconstruct, VoleCommitmentCRef},
     ByteEncoding, Error,
 };
 
@@ -308,10 +308,7 @@ trait FaestHash {
     /// Generate `r` and `iv`
     fn hash_r_iv(r: &mut [u8], iv: &mut IV, key: &[u8], mu: &[u8], rho: &[u8]);
     /// Generate first challange
-    fn hash_challenge_1<I, T>(chall1: &mut [u8], mu: &[u8], hcom: &[u8], c: I, iv: &[u8])
-    where
-        I: Iterator<Item = T>,
-        T: AsRef<[u8]>;
+    fn hash_challenge_1(chall1: &mut [u8], mu: &[u8], hcom: &[u8], c: &[u8], iv: &[u8]);
     /// Generate second challenge
     fn hash_challenge_2(chall2: &mut [u8], chall1: &[u8], u_t: &[u8], hv: &[u8], d: &[u8]);
     /// Generate third challenge
@@ -341,17 +338,11 @@ where
         h3_reader.read(iv);
     }
 
-    fn hash_challenge_1<I, T>(chall1: &mut [u8], mu: &[u8], hcom: &[u8], c: I, iv: &[u8])
-    where
-        I: Iterator<Item = T>,
-        T: AsRef<[u8]>,
-    {
+    fn hash_challenge_1(chall1: &mut [u8], mu: &[u8], hcom: &[u8], c: &[u8], iv: &[u8]) {
         let mut h2_hasher = Self::h2_init();
         h2_hasher.update(mu);
         h2_hasher.update(hcom);
-        for buf in c {
-            h2_hasher.update(buf.as_ref());
-        }
+        h2_hasher.update(c);
         h2_hasher.update(iv);
         h2_hasher.finish().read(chall1);
     }
@@ -413,18 +404,19 @@ fn sign<P, O>(
     let mut iv = IV::default();
     RO::<P>::hash_r_iv(&mut r, &mut iv, &sk.owf_key, &mu, rho);
 
-    let (hcom, decom, c, u, gv) =
-        volecommit::<<O::BaseParams as BaseParameters>::VC, P::Tau, O::LHATBYTES>(&r, &iv);
+    let volecommit_cs =
+        &mut signature[..O::LHATBYTES::USIZE * (<P::Tau as TauParameters>::Tau::USIZE - 1)];
+    let (hcom, decom, u, gv) = volecommit::<
+        <O::BaseParams as BaseParameters>::VC,
+        P::Tau,
+        O::LHATBYTES,
+    >(VoleCommitmentCRef::new(volecommit_cs), &r, &iv);
     let mut chall1 =
         GenericArray::<u8, <<O as OWFParameters>::BaseParams as BaseParameters>::Chall1>::default();
-    RO::<P>::hash_challenge_1(&mut chall1, &mu, &hcom, c.iter(), &iv);
-
-    // write c and drop it
-    let mut signature = signature.as_mut_slice();
-    for x in c.into_iter() {
-        signature.write_all(&x).unwrap();
-    }
+    RO::<P>::hash_challenge_1(&mut chall1, &mu, &hcom, volecommit_cs, &iv);
 
+    let signature =
+        &mut signature[O::LHATBYTES::USIZE * (<P::Tau as TauParameters>::Tau::USIZE - 1)..];
     let (u_t, hv) = {
         let vole_hasher = VoleHasher::<P>::new_vole_hasher(&chall1);
         let u_t = vole_hasher.process(&u);
@@ -542,7 +534,7 @@ where
     let mut chall1 =
         GenericArray::<u8, <<O as OWFParameters>::BaseParams as BaseParameters>::Chall1>::default();
     let c = &sigma[..O::LHATBYTES::USIZE * (<P::Tau as TauParameters>::Tau::USIZE - 1)];
-    RO::<P>::hash_challenge_1(&mut chall1, &mu, &hcom, [c].into_iter(), iv);
+    RO::<P>::hash_challenge_1(&mut chall1, &mu, &hcom, c, iv);
 
     let vole_hasher = VoleHasher::<P>::new_vole_hasher(&chall1);
     let def = GenericArray::default();
diff --git a/src/parameter.rs b/src/parameter.rs
index e60e52f..4b85f14 100644
--- a/src/parameter.rs
+++ b/src/parameter.rs
@@ -681,7 +681,6 @@ impl OWFParameters for OWF256EM {
 
 pub(crate) trait TauParameters {
     type Tau: ArrayLength;
-    type TauMinus1: ArrayLength;
     type K0: ArrayLength;
     type K1: ArrayLength;
     type Tau0: ArrayLength;
@@ -713,7 +712,6 @@ pub(crate) struct Tau128Small;
 
 impl TauParameters for Tau128Small {
     type Tau = U11;
-    type TauMinus1 = Diff<Self::Tau, U1>;
     type K0 = U12;
     type K1 = U11;
     type Tau0 = U7;
@@ -725,7 +723,6 @@ pub(crate) struct Tau128Fast;
 
 impl TauParameters for Tau128Fast {
     type Tau = U16;
-    type TauMinus1 = Diff<Self::Tau, U1>;
     type K0 = U8;
     type K1 = U8;
     type Tau0 = U8;
@@ -737,7 +734,6 @@ pub(crate) struct Tau192Small;
 
 impl TauParameters for Tau192Small {
     type Tau = U16;
-    type TauMinus1 = Diff<Self::Tau, U1>;
     type K0 = U12;
     type K1 = U12;
     type Tau0 = U8;
@@ -749,7 +745,6 @@ pub(crate) struct Tau192Fast;
 
 impl TauParameters for Tau192Fast {
     type Tau = U24;
-    type TauMinus1 = Diff<Self::Tau, U1>;
     type K0 = U8;
     type K1 = U8;
     type Tau0 = U12;
@@ -761,7 +756,6 @@ pub(crate) struct Tau256Small;
 
 impl TauParameters for Tau256Small {
     type Tau = U22;
-    type TauMinus1 = Diff<Self::Tau, U1>;
     type K0 = U12;
     type K1 = U11;
     type Tau0 = U14;
@@ -773,7 +767,6 @@ pub(crate) struct Tau256Fast;
 
 impl TauParameters for Tau256Fast {
     type Tau = U32;
-    type TauMinus1 = Diff<Self::Tau, U1>;
     type K0 = U8;
     type K1 = U8;
     type Tau0 = U16;
diff --git a/src/vole.rs b/src/vole.rs
index a2cb290..9bf7525 100644
--- a/src/vole.rs
+++ b/src/vole.rs
@@ -1,4 +1,8 @@
-use std::iter::zip;
+use std::{
+    iter::zip,
+    marker::PhantomData,
+    ops::{Index, IndexMut},
+};
 
 use generic_array::{typenum::Unsigned, ArrayLength, GenericArray};
 
@@ -48,8 +52,41 @@ where
     (r[(d % 2) * n].clone(), v)
 }
 
+/// Reference to storage area in signature for all `c`s.
+pub(crate) struct VoleCommitmentCRef<'a, LH>(&'a mut [u8], PhantomData<LH>);
+
+impl<'a, LH> Index<usize> for VoleCommitmentCRef<'a, LH>
+where
+    LH: ArrayLength,
+{
+    type Output = [u8];
+
+    fn index(&self, index: usize) -> &Self::Output {
+        &self.0[index * LH::USIZE..(index + 1) * LH::USIZE]
+    }
+}
+
+impl<'a, LH> IndexMut<usize> for VoleCommitmentCRef<'a, LH>
+where
+    LH: ArrayLength,
+{
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.0[index * LH::USIZE..(index + 1) * LH::USIZE]
+    }
+}
+
+impl<'a, LH> VoleCommitmentCRef<'a, LH>
+where
+    LH: ArrayLength,
+{
+    pub(crate) fn new(buffer: &'a mut [u8]) -> Self {
+        Self(buffer, PhantomData)
+    }
+}
+
 #[allow(clippy::type_complexity)]
 pub fn volecommit<VC, Tau, LH>(
+    mut c: VoleCommitmentCRef<LH>,
     r: &GenericArray<u8, VC::Lambda>,
     iv: &IV,
 ) -> (
@@ -64,7 +101,6 @@ pub fn volecommit<VC, Tau, LH>(
             Tau::Tau,
         >,
     >,
-    Box<GenericArray<GenericArray<u8, LH>, Tau::TauMinus1>>,
     Box<GenericArray<u8, LH>>,
     Box<GenericArray<Vec<GenericArray<u8, LH>>, Tau::Tau>>,
 )
@@ -77,7 +113,6 @@ where
     let mut decom = GenericArray::default_boxed();
     let mut u0 = GenericArray::<u8, LH>::default_boxed();
     let mut v = GenericArray::default_boxed();
-    let mut c = GenericArray::<GenericArray<u8, LH>, Tau::TauMinus1>::default_boxed();
 
     let mut hasher = VC::RO::h1_init();
     for i in 0..Tau::Tau::USIZE {
@@ -100,7 +135,7 @@ where
         }
     }
 
-    (hasher.finish().read_into(), decom, c, u0, v)
+    (hasher.finish().read_into(), decom, u0, v)
 }
 
 #[allow(clippy::type_complexity)]
@@ -181,6 +216,24 @@ mod test {
         u: Vec<u8>,
     }
 
+    fn volecommit<VC, Tau, LH>(
+        r: &GenericArray<u8, VC::Lambda>,
+        iv: &IV,
+    ) -> (
+        GenericArray<u8, VC::LambdaTimes2>,
+        Box<GenericArray<u8, LH>>,
+    )
+    where
+        Tau: TauParameters,
+        VC: VectorCommitment,
+        LH: ArrayLength,
+    {
+        let mut c = vec![0; LH::USIZE * (Tau::Tau::USIZE - 1)];
+        let ret =
+            super::volecommit::<VC, Tau, LH>(VoleCommitmentCRef::new(c.as_mut_slice()), r, iv);
+        (ret.0, ret.2)
+    }
+
     #[test]
     fn volecommit_test() {
         let database: Vec<DataVoleCommit> = read_test_data("DataVoleCommit.json");
@@ -196,7 +249,7 @@ mod test {
                             &GenericArray::generate(|idx| idx as u8), &IV::default()
                         );
                         assert_eq!(res.0.as_slice(), &data.hcom);
-                        assert_eq!(res.3.as_slice(), &data.u);
+                        assert_eq!(res.1.as_slice(), &data.u);
                     } else {
                         let res = volecommit::<
                             VC<FAEST128fParameters>,
@@ -206,7 +259,7 @@ mod test {
                             &GenericArray::generate(|idx| idx as u8), &IV::default()
                         );
                         assert_eq!(res.0.as_slice(), &data.hcom);
-                        assert_eq!(res.3.as_slice(), &data.u);
+                        assert_eq!(res.1.as_slice(), &data.u);
                     }
                 } else if data.k0[0] == 12 {
                     let res = volecommit::<
@@ -217,7 +270,7 @@ mod test {
                         &GenericArray::generate(|idx| idx as u8), &IV::default()
                     );
                     assert_eq!(res.0.as_slice(), &data.hcom);
-                    assert_eq!(res.3.as_slice(), &data.u);
+                    assert_eq!(res.1.as_slice(), &data.u);
                 } else {
                     let res = volecommit::<
                         VC<FAESTEM128fParameters>,
@@ -227,7 +280,7 @@ mod test {
                         &GenericArray::generate(|idx| idx as u8), &IV::default()
                     );
                     assert_eq!(res.0.as_slice(), &data.hcom);
-                    assert_eq!(res.3.as_slice(), &data.u);
+                    assert_eq!(res.1.as_slice(), &data.u);
                 }
             } else if data.lambdabytes[0] == 24 {
                 if data.u.len() == 458 {
@@ -240,7 +293,7 @@ mod test {
                             &GenericArray::generate(|idx| idx as u8), &IV::default()
                         );
                         assert_eq!(res.0.as_slice(), &data.hcom);
-                        assert_eq!(res.3.as_slice(), &data.u);
+                        assert_eq!(res.1.as_slice(), &data.u);
                     } else {
                         let res = volecommit::<
                             VC<FAEST192fParameters>,
@@ -250,7 +303,7 @@ mod test {
                             &GenericArray::generate(|idx| idx as u8), &IV::default()
                         );
                         assert_eq!(res.0.as_slice(), &data.hcom);
-                        assert_eq!(res.3.as_slice(), &data.u);
+                        assert_eq!(res.1.as_slice(), &data.u);
                     }
                 } else if data.k0[0] == 12 {
                     let res = volecommit::<
@@ -261,7 +314,7 @@ mod test {
                         &GenericArray::generate(|idx| idx as u8), &IV::default()
                     );
                     assert_eq!(res.0.as_slice(), &data.hcom);
-                    assert_eq!(res.3.as_slice(), &data.u);
+                    assert_eq!(res.1.as_slice(), &data.u);
                 } else {
                     let res = volecommit::<
                         VC<FAESTEM192fParameters>,
@@ -271,7 +324,7 @@ mod test {
                         &GenericArray::generate(|idx| idx as u8), &IV::default()
                     );
                     assert_eq!(res.0.as_slice(), &data.hcom);
-                    assert_eq!(res.3.as_slice(), &data.u);
+                    assert_eq!(res.1.as_slice(), &data.u);
                 }
             } else if data.u.len() == 566 {
                 if data.k0[0] == 12 {
@@ -283,7 +336,7 @@ mod test {
                         &GenericArray::generate(|idx| idx as u8), &IV::default()
                     );
                     assert_eq!(res.0.as_slice(), &data.hcom);
-                    assert_eq!(res.3.as_slice(), &data.u);
+                    assert_eq!(res.1.as_slice(), &data.u);
                 } else {
                     let res = volecommit::<
                         VC<FAEST256fParameters>,
@@ -293,7 +346,7 @@ mod test {
                         &GenericArray::generate(|idx| idx as u8), &IV::default()
                     );
                     assert_eq!(res.0.as_slice(), &data.hcom);
-                    assert_eq!(res.3.as_slice(), &data.u);
+                    assert_eq!(res.1.as_slice(), &data.u);
                 }
             } else if data.k0[0] == 12 {
                 let res =
@@ -303,7 +356,7 @@ mod test {
                         LH<FAESTEM256sParameters>,
                     >(&GenericArray::generate(|idx| idx as u8), &IV::default());
                 assert_eq!(res.0.as_slice(), &data.hcom);
-                assert_eq!(res.3.as_slice(), &data.u);
+                assert_eq!(res.1.as_slice(), &data.u);
             } else {
                 let res =
                     volecommit::<
@@ -312,7 +365,7 @@ mod test {
                         LH<FAESTEM256fParameters>,
                     >(&GenericArray::generate(|idx| idx as u8), &IV::default());
                 assert_eq!(res.0.as_slice(), &data.hcom);
-                assert_eq!(res.3.as_slice(), &data.u);
+                assert_eq!(res.1.as_slice(), &data.u);
             }
         }
     }