diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..580b368
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,39 @@
+[package]
+name = "fold-babyjubjubs"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+ark-bn254 = { version = "0.5.0", features = ["r1cs"] }
+ark-grumpkin = {version="0.5.0", features=["r1cs"]}
+ark-ec = "0.5.0"
+ark-ff = "0.5.0"
+ark-r1cs-std = { version = "0.5.0", default-features = false }
+ark-relations = { version = "0.5.0", default-features = false }
+ark-crypto-primitives = { version = "^0.5.0", default-features = false, features = [
+    "r1cs",
+    "sponge",
+    "crh",
+] }
+ark-std = "0.5.0"
+rand = "0.8.5"
+rand_core = {version = "0.6", default-features = false}
+
+# Note: for testing purposes we use the 'light-test' feature when importing
+# Sonobe's folding-schemes, but for a real-world usage it must be used without
+# this feature (but then the DeciderETH circuit is bigger and takes more time
+# to compute).
+folding-schemes = { git = "https://github.com/privacy-scaling-explorations/sonobe", package = "folding-schemes", features=["light-test"], rev="964f9b6de91283c2bf12ffdd7578125dc999104a"}
+# folding-schemes = { path = "../../sonobe/sonobe_FCIRCUIT-EXTINP/folding-schemes", package = "folding-schemes", features=["light-test"]}
+blake2 = "0.10"
+arkeddsa = { git = "https://github.com/arnaucube/arkeddsa", features=["r1cs"], rev="67c077e0e564d5f8d193a44f67357dfd1180cb64"}
+# arkeddsa = { path = "../arkeddsa_TE-to-C", features=["r1cs"]}
+
+
+
+
+[dev-dependencies]
+
+[features]
+default = []
+
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..245499e
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2023 Privacy & Scaling Explorations (formerly known as appliedzkp)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/src/fcircuit.rs b/src/fcircuit.rs
new file mode 100644
index 0000000..fb7e58c
--- /dev/null
+++ b/src/fcircuit.rs
@@ -0,0 +1,272 @@
+use ark_crypto_primitives::sponge::{poseidon::PoseidonConfig, Absorb};
+use ark_ec::CurveGroup;
+use ark_ff::{BigInteger, Field, PrimeField};
+use ark_r1cs_std::alloc::{AllocVar, AllocationMode};
+use ark_r1cs_std::prelude::CurveVar;
+use ark_r1cs_std::{
+    boolean::Boolean,
+    eq::EqGadget,
+    fields::{fp::FpVar, FieldVar},
+};
+use ark_relations::r1cs::{ConstraintSystemRef, Namespace, SynthesisError};
+use ark_std::{marker::PhantomData, Zero};
+use core::borrow::Borrow;
+use std::fmt::Debug;
+
+use arkeddsa::{constraints::verify, signature::Signature, PublicKey};
+use folding_schemes::{frontend::FCircuit, Error};
+
+pub type CF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;
+
+/// Test circuit to be folded
+#[derive(Clone, Debug)]
+pub struct FoldSigsStepCircuit<
+    F: PrimeField,
+    C: CurveGroup,
+    GC: CurveVar<C, F>,
+    const SIGS_PER_STEP: usize,
+> {
+    _c: PhantomData<C>,
+    _gc: PhantomData<GC>,
+    config: PoseidonConfig<F>,
+}
+impl<F: PrimeField, C: CurveGroup, GC: CurveVar<C, F>, const SIGS_PER_STEP: usize> FCircuit<F>
+    for FoldSigsStepCircuit<F, C, GC, SIGS_PER_STEP>
+where
+    F: Absorb,
+    C: CurveGroup<BaseField = F>,
+{
+    type Params = PoseidonConfig<F>;
+    type ExternalInputs = VecExtInp<C, SIGS_PER_STEP>;
+    type ExternalInputsVar = VecExtInpVar<C, GC, SIGS_PER_STEP>;
+
+    fn new(config: Self::Params) -> Result<Self, Error> {
+        Ok(Self {
+            _c: PhantomData,
+            _gc: PhantomData,
+            config,
+        })
+    }
+    fn state_len(&self) -> usize {
+        1
+    }
+    fn generate_step_constraints(
+        &self,
+        cs: ConstraintSystemRef<F>,
+        _i: usize,
+        z_i: Vec<FpVar<F>>,
+        external_inputs: Self::ExternalInputsVar,
+    ) -> Result<Vec<FpVar<F>>, SynthesisError> {
+        let mut count = z_i[0].clone();
+        for i in 0..SIGS_PER_STEP {
+            let e = external_inputs.0[i].clone();
+            let res = verify::<C, GC>(
+                cs.clone(),
+                self.config.clone(),
+                e.pk,
+                (e.sig_r, e.sig_s),
+                e.msg,
+            )?;
+            res.enforce_equal(&Boolean::<F>::TRUE)?;
+            count = count.clone() + FpVar::<F>::one();
+        }
+
+        Ok(vec![count])
+    }
+}
+
+// recall, here C = ed_on_bn254, so C::BaseField = BN254::ScalarField
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct ExtInp<C: CurveGroup> {
+    msg: CF<C>,
+    pk: PublicKey<C>,
+    sig: Signature<C>,
+}
+impl<C: CurveGroup> Default for ExtInp<C> {
+    fn default() -> Self {
+        Self {
+            msg: CF::<C>::zero(),
+            pk: PublicKey(C::zero().into_affine()),
+            sig: Signature::new(C::zero().into_affine(), C::ScalarField::zero()),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct VecExtInp<C: CurveGroup, const SIGS_PER_STEP: usize>(Vec<ExtInp<C>>);
+impl<C: CurveGroup, const SIGS_PER_STEP: usize> Default for VecExtInp<C, SIGS_PER_STEP> {
+    fn default() -> Self {
+        VecExtInp(vec![ExtInp::default(); SIGS_PER_STEP])
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct ExtInpVar<C: CurveGroup, GC: CurveVar<C, CF<C>>> {
+    msg: FpVar<CF<C>>,
+    pk: GC,
+    sig_r: GC,
+    sig_s: Vec<Boolean<CF<C>>>,
+}
+impl<C: CurveGroup, GC: CurveVar<C, CF<C>>> Default for ExtInpVar<C, GC> {
+    fn default() -> Self {
+        Self {
+            msg: FpVar::<CF<C>>::zero(),
+            pk: GC::zero(),
+            sig_r: GC::zero(),
+            sig_s: vec![Boolean::<CF<C>>::FALSE; 253], // TODO 253-> fieldbitsize
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct VecExtInpVar<C: CurveGroup, GC: CurveVar<C, CF<C>>, const SIGS_PER_STEP: usize>(
+    Vec<ExtInpVar<C, GC>>,
+);
+impl<C: CurveGroup, GC: CurveVar<C, CF<C>>, const SIGS_PER_STEP: usize> Default
+    for VecExtInpVar<C, GC, SIGS_PER_STEP>
+{
+    fn default() -> Self {
+        VecExtInpVar(vec![ExtInpVar::default(); SIGS_PER_STEP])
+    }
+}
+
+impl<C, GC, const SIGS_PER_STEP: usize> AllocVar<VecExtInp<C, SIGS_PER_STEP>, CF<C>>
+    for VecExtInpVar<C, GC, SIGS_PER_STEP>
+where
+    C: CurveGroup,
+    GC: CurveVar<C, CF<C>>,
+{
+    fn new_variable<T: Borrow<VecExtInp<C, SIGS_PER_STEP>>>(
+        cs: impl Into<Namespace<CF<C>>>,
+        f: impl FnOnce() -> Result<T, SynthesisError>,
+        mode: AllocationMode,
+    ) -> Result<Self, SynthesisError> {
+        f().and_then(|val| {
+            let cs = cs.into();
+
+            let mut v = vec![];
+            for e in val.borrow().0.iter() {
+                let msg = FpVar::<CF<C>>::new_variable(cs.clone(), || Ok(e.msg), mode)?;
+                let pk = GC::new_variable(cs.clone(), || Ok(e.pk.0), mode)?;
+                let sig_r = GC::new_variable(cs.clone(), || Ok(e.sig.r), mode)?;
+                let sig_s = Vec::<Boolean<CF<C>>>::new_variable(
+                    cs.clone(),
+                    || Ok(e.sig.s.into_bigint().to_bits_le()),
+                    mode,
+                )?;
+                v.push(ExtInpVar {
+                    msg,
+                    pk,
+                    sig_r,
+                    sig_s,
+                });
+            }
+
+            Ok(Self(v))
+        })
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use super::*;
+    use ark_bn254::Fr;
+    use ark_ec::AdditiveGroup;
+    use ark_r1cs_std::{alloc::AllocVar, R1CSVar};
+    use ark_relations::r1cs::ConstraintSystem;
+    use ark_std::rand::Rng;
+    use rand_core::CryptoRngCore;
+    use std::str::FromStr;
+
+    use folding_schemes::transcript::poseidon::poseidon_canonical_config;
+
+    use arkeddsa::{
+        ed_on_bn254_twist::{constraints::EdwardsVar, EdwardsProjective},
+        SigningKey,
+    };
+
+    pub fn gen_signatures<R: Rng + CryptoRngCore, const SIGS_PER_STEP: usize>(
+        rng: &mut R,
+        poseidon_config: &PoseidonConfig<Fr>,
+        steps: usize,
+    ) -> Vec<VecExtInp<EdwardsProjective, SIGS_PER_STEP>> {
+        let mut r = vec![];
+        for _ in 0..steps {
+            let mut res: Vec<ExtInp<EdwardsProjective>> = Vec::new();
+            for _ in 0..SIGS_PER_STEP {
+                let sk =
+                    SigningKey::<EdwardsProjective>::generate::<blake2::Blake2b512>(rng).unwrap();
+                let msg = Fr::from_str("12345").unwrap();
+                let sig = sk
+                    .sign::<blake2::Blake2b512>(&poseidon_config, &msg)
+                    .unwrap();
+                let pk = sk.public_key();
+                pk.verify(&poseidon_config, &msg, &sig).unwrap();
+                res.push(ExtInp {
+                    msg,
+                    pk: pk.clone(),
+                    sig,
+                });
+            }
+            r.push(VecExtInp(res));
+        }
+        r
+    }
+
+    #[test]
+    fn test_sig() {
+        const SIGS_PER_STEP: usize = 10;
+        let mut rng = rand::rngs::OsRng;
+        let poseidon_config = poseidon_canonical_config::<Fr>();
+
+        const N: usize = 1;
+        let ext_inps =
+            gen_signatures::<rand::rngs::OsRng, SIGS_PER_STEP>(&mut rng, &poseidon_config, 1);
+        let e = ext_inps[0].0[0].clone();
+        e.pk.verify(&poseidon_config, &e.msg, &e.sig).unwrap();
+    }
+
+    fn ensure_fcircuit_trait<FC: FCircuit<Fr>>(params: FC::Params) {
+        let _ = FC::new(params);
+    }
+
+    // test to check that the Sha256FCircuit computes the same values inside and outside the circuit
+    #[test]
+    fn test_fcircuit() {
+        const SIGS_PER_STEP: usize = 10;
+        let mut rng = rand::rngs::OsRng;
+        let poseidon_config = poseidon_canonical_config::<Fr>();
+
+        let ext_inps =
+            gen_signatures::<rand::rngs::OsRng, SIGS_PER_STEP>(&mut rng, &poseidon_config, 1);
+        let ext_inps = ext_inps[0].clone();
+
+        // here `Fr` is the BN254::G1::Fr = ed_on_bn254_twist::EdwardsProjective::Fq
+        let cs = ConstraintSystem::<Fr>::new_ref();
+
+        type FC = FoldSigsStepCircuit<Fr, EdwardsProjective, EdwardsVar, SIGS_PER_STEP>;
+        ensure_fcircuit_trait::<FC>(poseidon_config.clone());
+
+        let circuit = FC::new(poseidon_config).unwrap();
+        let z_i = vec![Fr::ZERO];
+
+        let external_inputs_var =
+            VecExtInpVar::<EdwardsProjective, EdwardsVar, SIGS_PER_STEP>::new_witness(
+                cs.clone(),
+                || Ok(ext_inps),
+            )
+            .unwrap();
+
+        let z_iVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(z_i)).unwrap();
+        let computed_z_i1Var = circuit
+            .generate_step_constraints(cs.clone(), 0, z_iVar.clone(), external_inputs_var)
+            .unwrap();
+        assert_eq!(
+            computed_z_i1Var.value().unwrap(),
+            vec![Fr::from(SIGS_PER_STEP as u32)]
+        );
+        assert!(cs.is_satisfied().unwrap());
+        dbg!(cs.num_constraints());
+        dbg!(&computed_z_i1Var.value().unwrap());
+    }
+}