diff --git a/spec/cox/pwhash_spec.cr b/spec/cox/pwhash_spec.cr
new file mode 100644
index 0000000..b7f61c9
--- /dev/null
+++ b/spec/cox/pwhash_spec.cr
@@ -0,0 +1,22 @@
+require "../spec_helper"
+
+describe Cox::Pwhash do
+  it "hashes and verifies a password" do
+    pwhash = Cox::Pwhash.new
+
+    # set to minimum to speed up tests
+    pwhash.memlimit = Cox::Pwhash::MEMLIMIT_MIN
+    pwhash.opslimit = Cox::Pwhash::OPSLIMIT_MIN
+
+    pass = "1234"
+    hash = pwhash.hash_str pass
+    pwhash.verify hash, pass
+    expect_raises(Cox::Pwhash::PasswordVerifyError) do
+      pwhash.verify hash, "5678"
+    end
+
+    pwhash.needs_rehash?(hash).should be_false
+    pwhash.opslimit = Cox::Pwhash::OPSLIMIT_MAX
+    pwhash.needs_rehash?(hash).should be_true
+  end
+end
diff --git a/src/cox/lib_sodium.cr b/src/cox/lib_sodium.cr
index 4d25991..03863c4 100644
--- a/src/cox/lib_sodium.cr
+++ b/src/cox/lib_sodium.cr
@@ -12,6 +12,15 @@ module Cox
     fun crypto_sign_bytes()          : LibC::SizeT
     fun crypto_kdf_keybytes()        : LibC::SizeT
     fun crypto_kdf_contextbytes()    : LibC::SizeT
+    fun crypto_pwhash_memlimit_min()     : LibC::SizeT
+    fun crypto_pwhash_memlimit_interactive()     : LibC::SizeT
+    fun crypto_pwhash_memlimit_max()     : LibC::SizeT
+    fun crypto_pwhash_opslimit_min()     : LibC::SizeT
+    fun crypto_pwhash_opslimit_interactive()     : LibC::SizeT
+    fun crypto_pwhash_opslimit_moderate()     : LibC::SizeT
+    fun crypto_pwhash_opslimit_sensitive()     : LibC::SizeT
+    fun crypto_pwhash_opslimit_max()     : LibC::SizeT
+    fun crypto_pwhash_strbytes()     : LibC::SizeT
 
     PUBLIC_KEY_BYTES  = crypto_box_publickeybytes()
     SECRET_KEY_BYTES  = crypto_box_secretkeybytes()
@@ -22,6 +31,7 @@ module Cox
     SIGNATURE_BYTES   = crypto_sign_bytes()
     KDF_KEY_BYTES     = crypto_kdf_keybytes()
     KDF_CONTEXT_BYTES = crypto_kdf_contextbytes()
+    PWHASH_STR_BYTES  = crypto_pwhash_strbytes()
 
     fun crypto_box_keypair(
       public_key_output : Pointer(LibC::UChar),
@@ -66,7 +76,6 @@ module Cox
       public_key   : Pointer(LibC::UChar)
     ) : LibC::Int
 
-
     fun crypto_kdf_derive_from_key(
       subkey    : Pointer(LibC::UChar),
       subkey_len    : LibC::SizeT,
@@ -74,5 +83,25 @@ module Cox
       ctx    : Pointer(LibC::UChar),
       key    : Pointer(LibC::UChar)
     ) : LibC::Int
+
+    fun crypto_pwhash_str(
+      outstr    : Pointer(LibC::UChar),
+      pass    : Pointer(LibC::UChar),
+      pass_size    : LibC::ULongLong,
+      optslimit    : LibC::ULongLong,
+      memlimit    : LibC::SizeT,
+    ) : LibC::Int
+
+    fun crypto_pwhash_str_verify(
+      str    : Pointer(LibC::UChar),
+      pass    : Pointer(LibC::UChar),
+      pass_size    : LibC::ULongLong,
+    ) : LibC::Int
+
+    fun crypto_pwhash_str_needs_rehash(
+      str    : Pointer(LibC::UChar),
+      optslimit    : LibC::ULongLong,
+      memlimit    : LibC::SizeT,
+    ) : LibC::Int
   end
 end
diff --git a/src/cox/pwhash.cr b/src/cox/pwhash.cr
new file mode 100644
index 0000000..944da48
--- /dev/null
+++ b/src/cox/pwhash.cr
@@ -0,0 +1,49 @@
+module Cox
+  class Pwhash
+    class PasswordVerifyError < Cox::Error
+    end
+
+    OPSLIMIT_MIN         = LibSodium.crypto_pwhash_opslimit_min
+    OPSLIMIT_INTERACTIVE = LibSodium.crypto_pwhash_opslimit_interactive
+    OPSLIMIT_MODERATE    = LibSodium.crypto_pwhash_opslimit_moderate
+    OPSLIMIT_SENSITIVE   = LibSodium.crypto_pwhash_opslimit_sensitive
+    OPSLIMIT_MAX         = LibSodium.crypto_pwhash_opslimit_max
+
+    MEMLIMIT_MIN         = LibSodium.crypto_pwhash_memlimit_min
+    MEMLIMIT_MAX         = LibSodium.crypto_pwhash_memlimit_max
+    MEMLIMIT_INTERACTIVE = LibSodium.crypto_pwhash_memlimit_interactive
+
+    property opslimit = OPSLIMIT_INTERACTIVE
+    property memlimit = MEMLIMIT_INTERACTIVE
+
+    def hash_str(pass)
+      outstr = Bytes.new LibSodium::PWHASH_STR_BYTES
+      if LibSodium.crypto_pwhash_str(outstr, pass, pass.bytesize, @opslimit, @memlimit) != 0
+        raise Cox::Error.new("crypto_pwhash_str")
+      end
+      outstr
+    end
+
+    def verify(str, pass)
+      # BUG: verify str length
+      case LibSodium.crypto_pwhash_str_verify(str, pass, pass.bytesize)
+      when 0
+        true
+      else
+        raise PasswordVerifyError.new
+      end
+    end
+
+    def needs_rehash?(str)
+      # BUG: verify str length
+      case LibSodium.crypto_pwhash_str_needs_rehash(str, @opslimit, @memlimit)
+      when 0
+        false
+      when 1
+        true
+      else
+        raise Cox::Error.new("crypto_pwhash_str_needs_rehash")
+      end
+    end
+  end
+end