diff --git a/src/core/mint/mint.zig b/src/core/mint/mint.zig
index be79feb..c003ed7 100644
--- a/src/core/mint/mint.zig
+++ b/src/core/mint/mint.zig
@@ -422,7 +422,7 @@ pub const Mint = struct {
         // check if keyset already in
         {
             self.keysets.lock.lockShared();
-            defer self.keysets.lock.lockShared();
+            defer self.keysets.lock.unlockShared();
 
             if (self.keysets.value.contains(id)) return;
         }
@@ -587,6 +587,115 @@ pub const Mint = struct {
 
         _ = try self.localstore.value.updateMintQuoteState(mint_quote.id, .paid);
     }
+
+    /// Blind Sign
+    pub fn blindSign(
+        self: *Mint,
+        gpa: std.mem.Allocator,
+        blinded_message: core.nuts.BlindedMessage,
+    ) !core.nuts.BlindSignature {
+        try self.ensureKeysetLoaded(blinded_message.keyset_id);
+
+        const keyset_info = try self
+            .localstore.value
+            .getKeysetInfo(gpa, blinded_message.keyset_id) orelse return error.UnknownKeySet;
+        errdefer keyset_info.deinit(gpa);
+
+        const active = self
+            .localstore
+            .value
+            .getActiveKeysetId(keyset_info.unit) orelse return error.InactiveKeyset;
+
+        // Check that the keyset is active and should be used to sign
+        if (!std.meta.eql(keyset_info.id, active)) {
+            return error.InactiveKeyset;
+        }
+
+        const keyset = v: {
+            self.keysets.lock.lock();
+            defer self.keysets.lock.unlock();
+
+            break :v self.keysets.value.get(blinded_message.keyset_id) orelse return error.UknownKeySet;
+        };
+
+        const key_pair = keyset.keys.inner.get(blinded_message.amount) orelse return error.AmountKey;
+
+        const c = try core.dhke.signMessage(
+            self.secp_ctx,
+            key_pair.secret_key,
+            blinded_message.blinded_secret,
+        );
+
+        const blinded_signature = try core.nuts.initBlindSignature(
+            self.secp_ctx,
+            blinded_message.amount,
+            c,
+            keyset_info.id,
+            blinded_message.blinded_secret,
+            key_pair.secret_key,
+        );
+
+        return blinded_signature;
+    }
+
+    /// Process mint request
+    pub fn processMintRequest(
+        self: *Mint,
+        gpa: std.mem.Allocator,
+        mint_request: core.nuts.nut04.MintBolt11Request,
+    ) !core.nuts.nut04.MintBolt11Response {
+        const quote_id = try zul.UUID.parse(&mint_request.quote);
+        const state = try self.localstore.value.updateMintQuoteState(quote_id.bin, .pending);
+
+        std.log.debug("process_mitn_request: quote_id {s}", .{quote_id.toHex(.lower)});
+        switch (state) {
+            .unpaid => return error.UnpaidQuote,
+            .pending => return error.PendingQuote,
+            .issued => return error.IssuedQuote,
+            .paid => {},
+        }
+
+        var blinded_messages = try std.ArrayList(secp256k1.PublicKey).initCapacity(gpa, mint_request.outputs.len);
+        errdefer blinded_messages.deinit();
+
+        for (mint_request.outputs) |b| {
+            blinded_messages.appendAssumeCapacity(b.blinded_secret);
+        }
+
+        const _blind_signatures = try self.localstore.value.getBlindSignatures(gpa, blinded_messages.items);
+        defer _blind_signatures.deinit();
+
+        for (_blind_signatures.items) |bs| {
+            if (bs != null) {
+                std.log.debug("output has already been signed", .{});
+                std.log.debug("Mint {x} did not succeed returning quote to Paid state", .{mint_request.quote});
+
+                _ = try self.localstore
+                    .value.updateMintQuoteState(quote_id.bin, .paid);
+                return error.BlindedMessageAlreadySigned;
+            }
+        }
+
+        var blind_signatures = try std.ArrayList(core.nuts.BlindSignature).initCapacity(gpa, mint_request.outputs.len);
+        errdefer blind_signatures.deinit();
+
+        for (mint_request.outputs) |blinded_message| {
+            const blind_signature = try self.blindSign(gpa, blinded_message);
+            blind_signatures.appendAssumeCapacity(blind_signature);
+        }
+
+        try self.localstore
+            .value
+            .addBlindSignatures(blinded_messages.items, blind_signatures.items);
+
+        _ = try self.localstore.value.updateMintQuoteState(quote_id.bin, .issued);
+
+        std.log.debug("process_mint_request: issued {s}", .{quote_id.toHex(.lower)});
+
+        return .{
+            .signatures = try blind_signatures.toOwnedSlice(),
+        };
+    }
 };
 
 /// Generate new [`MintKeySetInfo`] from path
diff --git a/src/core/mint/types.zig b/src/core/mint/types.zig
index cf7aec7..d82b2f7 100644
--- a/src/core/mint/types.zig
+++ b/src/core/mint/types.zig
@@ -26,6 +26,16 @@ pub const MintQuote = struct {
     /// Value used by ln backend to look up state of request
     request_lookup_id: []const u8,
 
+    /// formatting mint quote
+    pub fn format(
+        self: MintQuote,
+        comptime _: []const u8,
+        _: std.fmt.FormatOptions,
+        writer: anytype,
+    ) !void {
+        try writer.print("{}", .{std.json.fmt(self, .{})});
+    }
+
     /// Create new [`MintQuote`]
     /// creating copy of arguments, so caller responsible on deinit resources
     pub fn initAlloc(
diff --git a/src/core/nuts/nut04/nut04.zig b/src/core/nuts/nut04/nut04.zig
index c7e676e..d267974 100644
--- a/src/core/nuts/nut04/nut04.zig
+++ b/src/core/nuts/nut04/nut04.zig
@@ -5,6 +5,8 @@ const std = @import("std");
 const zul = @import("zul");
 
 const CurrencyUnit = @import("../nut00/nut00.zig").CurrencyUnit;
+const BlindedMessage = @import("../nut00/nut00.zig").BlindedMessage;
+const BlindSignature = @import("../nut00/nut00.zig").BlindSignature;
 const Proof = @import("../nut00/nut00.zig").Proof;
 const PaymentMethod = @import("../nut00/nut00.zig").PaymentMethod;
 const MintQuote = @import("../../mint/types.zig").MintQuote;
@@ -191,3 +193,17 @@ pub const MintQuoteBolt11Response = struct {
         };
     }
 };
+
+/// Mint response [NUT-04]
+pub const MintBolt11Response = struct {
+    /// Blinded Signatures
+    signatures: []const BlindSignature,
+};
+
+/// Mint request [NUT-04]
+pub const MintBolt11Request = struct {
+    /// Quote id
+    quote: [36]u8,
+    /// Outputs
+    outputs: []const BlindedMessage,
+};
diff --git a/src/router/router.zig b/src/router/router.zig
index 69b3a28..d6d3cdd 100644
--- a/src/router/router.zig
+++ b/src/router/router.zig
@@ -55,6 +55,7 @@ pub fn createMintServer(
 
     router.post("/v1/mint/quote/bolt11", router_handlers.getMintBolt11Quote, .{});
     router.post("/v1/melt/quote/bolt11", router_handlers.getMeltBolt11Quote, .{});
+    router.post("/v1/mint/bolt11", router_handlers.postMintBolt11, .{});
     return srv;
 }
 
diff --git a/src/router/router_handlers.zig b/src/router/router_handlers.zig
index 09afbe4..6bb725a 100644
--- a/src/router/router_handlers.zig
+++ b/src/router/router_handlers.zig
@@ -116,6 +116,26 @@ pub fn getMintBolt11Quote(
     );
 }
 
+pub fn postMintBolt11(
+    state: MintState,
+    req: *httpz.Request,
+    res: *httpz.Response,
+) !void {
+    errdefer std.log.debug("{any}", .{@errorReturnTrace()});
+
+    const payload = try req.json(core.nuts.nut04.MintBolt11Request) orelse return error.WrongRequest;
+
+    const r = state.mint
+        .processMintRequest(res.arena, payload) catch |err| {
+        // TODO print self error
+        std.log.err("could not process mint {any}, err {any}", .{ payload, err });
+
+        return err;
+    };
+
+    return try res.json(r, .{});
+}
+
 pub fn getMeltBolt11Quote(
     state: MintState,
     req: *httpz.Request,