diff --git a/dsa.go b/dsa.go
new file mode 100644
index 0000000..4742308
--- /dev/null
+++ b/dsa.go
@@ -0,0 +1,44 @@
+package rfc6979
+
+import (
+	"crypto/dsa"
+	"math/big"
+)
+
+// Sign signs an arbitrary length hash (which should be the result of hashing a
+// larger message) using the private key, priv. It returns the signature as a
+// pair of integers.
+//
+// Note that FIPS 186-3 section 4.6 specifies that the hash should be truncated
+// to the byte-length of the subgroup. This function does not perform that
+// truncation itself.
+func SignDSA(priv *dsa.PrivateKey, hash []byte, alg HashAlgorithm) (r, s *big.Int, err error) {
+	n := priv.Q.BitLen()
+	if n&7 != 0 {
+		err = dsa.ErrInvalidPublicKey
+		return
+	}
+	n >>= 3
+
+	generateSecret(priv.Q, priv.X, alg, hash, func(k *big.Int) bool {
+		kInv := new(big.Int).ModInverse(k, priv.Q)
+		r = new(big.Int).Exp(priv.G, k, priv.P)
+		r.Mod(r, priv.Q)
+
+		if r.Sign() == 0 {
+			return false
+		}
+
+		z := new(big.Int).SetBytes(hash)
+
+		s = new(big.Int).Mul(priv.X, r)
+		s.Add(s, z)
+		s.Mod(s, priv.Q)
+		s.Mul(s, kInv)
+		s.Mod(s, priv.Q)
+
+		return s.Sign() != 0
+	})
+
+	return
+}
diff --git a/dsa_test.go b/dsa_test.go
new file mode 100644
index 0000000..dc6c7f0
--- /dev/null
+++ b/dsa_test.go
@@ -0,0 +1,264 @@
+package rfc6979
+
+import (
+	"crypto/dsa"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"encoding/hex"
+	"math/big"
+	"testing"
+)
+
+type dsaFixture struct {
+	name    string
+	key     *dsaKey
+	alg     HashAlgorithm
+	message string
+	r, s    string
+}
+
+type dsaKey struct {
+	key      *dsa.PrivateKey
+	subgroup int
+}
+
+var dsa1024 = &dsaKey{
+	key: &dsa.PrivateKey{
+		PublicKey: dsa.PublicKey{
+			Parameters: dsa.Parameters{
+				P: dsaLoadInt("86F5CA03DCFEB225063FF830A0C769B9DD9D6153AD91D7CE27F787C43278B447E6533B86B18BED6E8A48B784A14C252C5BE0DBF60B86D6385BD2F12FB763ED8873ABFD3F5BA2E0A8C0A59082EAC056935E529DAF7C610467899C77ADEDFC846C881870B7B19B2B58F9BE0521A17002E3BDD6B86685EE90B3D9A1B02B782B1779"),
+				Q: dsaLoadInt("996F967F6C8E388D9E28D01E205FBA957A5698B1"),
+				G: dsaLoadInt("07B0F92546150B62514BB771E2A0C0CE387F03BDA6C56B505209FF25FD3C133D89BBCD97E904E09114D9A7DEFDEADFC9078EA544D2E401AEECC40BB9FBBF78FD87995A10A1C27CB7789B594BA7EFB5C4326A9FE59A070E136DB77175464ADCA417BE5DCE2F40D10A46A3A3943F26AB7FD9C0398FF8C76EE0A56826A8A88F1DBD"),
+			},
+			Y: dsaLoadInt("5DF5E01DED31D0297E274E1691C192FE5868FEF9E19A84776454B100CF16F65392195A38B90523E2542EE61871C0440CB87C322FC4B4D2EC5E1E7EC766E1BE8D4CE935437DC11C3C8FD426338933EBFE739CB3465F4D3668C5E473508253B1E682F65CBDC4FAE93C2EA212390E54905A86E2223170B44EAA7DA5DD9FFCFB7F3B"),
+		},
+		X: dsaLoadInt("411602CB19A6CCC34494D79D98EF1E7ED5AF25F7"),
+	},
+	subgroup: 160,
+}
+
+var dsa2048 = &dsaKey{
+	key: &dsa.PrivateKey{
+		PublicKey: dsa.PublicKey{
+			Parameters: dsa.Parameters{
+				P: dsaLoadInt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
+				Q: dsaLoadInt("F2C3119374CE76C9356990B465374A17F23F9ED35089BD969F61C6DDE9998C1F"),
+				G: dsaLoadInt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
+			},
+			Y: dsaLoadInt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
+		},
+		X: dsaLoadInt("69C7548C21D0DFEA6B9A51C9EAD4E27C33D3B3F180316E5BCAB92C933F0E4DBC"),
+	},
+	subgroup: 256,
+}
+
+var dsaFixtures = []dsaFixture{
+	// DSA, 1024 Bits
+	// https://tools.ietf.org/html/rfc6979#appendix-A.2.1
+	dsaFixture{
+		name:    "1024/SHA-1 #1",
+		key:     dsa1024,
+		alg:     sha1.New,
+		message: "sample",
+		r:       "2E1A0C2562B2912CAAF89186FB0F42001585DA55",
+		s:       "29EFB6B0AFF2D7A68EB70CA313022253B9A88DF5",
+	},
+	dsaFixture{
+		name:    "1024/SHA-224 #1",
+		key:     dsa1024,
+		alg:     sha256.New224,
+		message: "sample",
+		r:       "4BC3B686AEA70145856814A6F1BB53346F02101E",
+		s:       "410697B92295D994D21EDD2F4ADA85566F6F94C1",
+	},
+	dsaFixture{
+		name:    "1024/SHA-256 #1",
+		key:     dsa1024,
+		alg:     sha256.New,
+		message: "sample",
+		r:       "81F2F5850BE5BC123C43F71A3033E9384611C545",
+		s:       "4CDD914B65EB6C66A8AAAD27299BEE6B035F5E89",
+	},
+	dsaFixture{
+		name:    "1024/SHA-384 #1",
+		key:     dsa1024,
+		alg:     sha512.New384,
+		message: "sample",
+		r:       "07F2108557EE0E3921BC1774F1CA9B410B4CE65A",
+		s:       "54DF70456C86FAC10FAB47C1949AB83F2C6F7595",
+	},
+	dsaFixture{
+		name:    "1024/SHA-512 #1",
+		key:     dsa1024,
+		alg:     sha512.New,
+		message: "sample",
+		r:       "16C3491F9B8C3FBBDD5E7A7B667057F0D8EE8E1B",
+		s:       "02C36A127A7B89EDBB72E4FFBC71DABC7D4FC69C",
+	},
+	dsaFixture{
+		name:    "1024/SHA-1 #2",
+		key:     dsa1024,
+		alg:     sha1.New,
+		message: "test",
+		r:       "42AB2052FD43E123F0607F115052A67DCD9C5C77",
+		s:       "183916B0230D45B9931491D4C6B0BD2FB4AAF088",
+	},
+	dsaFixture{
+		name:    "1024/SHA-224 #2",
+		key:     dsa1024,
+		alg:     sha256.New224,
+		message: "test",
+		r:       "6868E9964E36C1689F6037F91F28D5F2C30610F2",
+		s:       "49CEC3ACDC83018C5BD2674ECAAD35B8CD22940F",
+	},
+	dsaFixture{
+		name:    "1024/SHA-256 #2",
+		key:     dsa1024,
+		alg:     sha256.New,
+		message: "test",
+		r:       "22518C127299B0F6FDC9872B282B9E70D0790812",
+		s:       "6837EC18F150D55DE95B5E29BE7AF5D01E4FE160",
+	},
+	dsaFixture{
+		name:    "1024/SHA-384 #2",
+		key:     dsa1024,
+		alg:     sha512.New384,
+		message: "test",
+		r:       "854CF929B58D73C3CBFDC421E8D5430CD6DB5E66",
+		s:       "91D0E0F53E22F898D158380676A871A157CDA622",
+	},
+	dsaFixture{
+		name:    "1024/SHA-512 #2",
+		key:     dsa1024,
+		alg:     sha512.New,
+		message: "test",
+		r:       "8EA47E475BA8AC6F2D821DA3BD212D11A3DEB9A0",
+		s:       "7C670C7AD72B6C050C109E1790008097125433E8",
+	},
+
+	// DSA, 2048 Bits
+	// https://tools.ietf.org/html/rfc6979#appendix-A.2.2
+	dsaFixture{
+		name:    "2048/SHA-1 #1",
+		key:     dsa2048,
+		alg:     sha1.New,
+		message: "sample",
+		r:       "3A1B2DBD7489D6ED7E608FD036C83AF396E290DBD602408E8677DAABD6E7445A",
+		s:       "D26FCBA19FA3E3058FFC02CA1596CDBB6E0D20CB37B06054F7E36DED0CDBBCCF",
+	},
+	dsaFixture{
+		name:    "2048/SHA-224 #1",
+		key:     dsa2048,
+		alg:     sha256.New224,
+		message: "sample",
+		r:       "DC9F4DEADA8D8FF588E98FED0AB690FFCE858DC8C79376450EB6B76C24537E2C",
+		s:       "A65A9C3BC7BABE286B195D5DA68616DA8D47FA0097F36DD19F517327DC848CEC",
+	},
+	dsaFixture{
+		name:    "2048/SHA-256 #1",
+		key:     dsa2048,
+		alg:     sha256.New,
+		message: "sample",
+		r:       "EACE8BDBBE353C432A795D9EC556C6D021F7A03F42C36E9BC87E4AC7932CC809",
+		s:       "7081E175455F9247B812B74583E9E94F9EA79BD640DC962533B0680793A38D53",
+	},
+	dsaFixture{
+		name:    "2048/SHA-384 #1",
+		key:     dsa2048,
+		alg:     sha512.New384,
+		message: "sample",
+		r:       "B2DA945E91858834FD9BF616EBAC151EDBC4B45D27D0DD4A7F6A22739F45C00B",
+		s:       "19048B63D9FD6BCA1D9BAE3664E1BCB97F7276C306130969F63F38FA8319021B",
+	},
+	dsaFixture{
+		name:    "2048/SHA-512 #1",
+		key:     dsa2048,
+		alg:     sha512.New,
+		message: "sample",
+		r:       "2016ED092DC5FB669B8EFB3D1F31A91EECB199879BE0CF78F02BA062CB4C942E",
+		s:       "D0C76F84B5F091E141572A639A4FB8C230807EEA7D55C8A154A224400AFF2351",
+	},
+	dsaFixture{
+		name:    "2048/SHA-1 #2",
+		key:     dsa2048,
+		alg:     sha1.New,
+		message: "test",
+		r:       "C18270A93CFC6063F57A4DFA86024F700D980E4CF4E2CB65A504397273D98EA0",
+		s:       "414F22E5F31A8B6D33295C7539C1C1BA3A6160D7D68D50AC0D3A5BEAC2884FAA",
+	},
+	dsaFixture{
+		name:    "2048/SHA-224 #2",
+		key:     dsa2048,
+		alg:     sha256.New224,
+		message: "test",
+		r:       "272ABA31572F6CC55E30BF616B7A265312018DD325BE031BE0CC82AA17870EA3",
+		s:       "E9CC286A52CCE201586722D36D1E917EB96A4EBDB47932F9576AC645B3A60806",
+	},
+	dsaFixture{
+		name:    "2048/SHA-256 #2",
+		key:     dsa2048,
+		alg:     sha256.New,
+		message: "test",
+		r:       "8190012A1969F9957D56FCCAAD223186F423398D58EF5B3CEFD5A4146A4476F0",
+		s:       "7452A53F7075D417B4B013B278D1BB8BBD21863F5E7B1CEE679CF2188E1AB19E",
+	},
+	dsaFixture{
+		name:    "2048/SHA-384 #2",
+		key:     dsa2048,
+		alg:     sha512.New384,
+		message: "test",
+		r:       "239E66DDBE8F8C230A3D071D601B6FFBDFB5901F94D444C6AF56F732BEB954BE",
+		s:       "6BD737513D5E72FE85D1C750E0F73921FE299B945AAD1C802F15C26A43D34961",
+	},
+	dsaFixture{
+		name:    "2048/SHA-512 #2",
+		key:     dsa2048,
+		alg:     sha512.New,
+		message: "test",
+		r:       "89EC4BB1400ECCFF8E7D9AA515CD1DE7803F2DAFF09693EE7FD1353E90A68307",
+		s:       "C9F0BDABCC0D880BB137A994CC7F3980CE91CC10FAF529FC46565B15CEA854E1",
+	},
+}
+
+func TestDSASignatures(t *testing.T) {
+	for _, f := range dsaFixtures {
+		testDsaFixture(&f, t)
+	}
+}
+
+func testDsaFixture(f *dsaFixture, t *testing.T) {
+	t.Logf("Testing %s", f.name)
+
+	digest := f.alg.digest([]byte(f.message))
+	g := f.key.subgroup / 8
+	if len(digest) > g {
+		digest = digest[0:g]
+	}
+
+	r, s, err := SignDSA(f.key.key, digest, f.alg)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	expectedR := dsaLoadInt(f.r)
+	expectedS := dsaLoadInt(f.s)
+
+	if r.Cmp(expectedR) != 0 {
+		t.Errorf("%s: Expected R of %X, got %X", f.name, expectedR, r)
+	}
+
+	if s.Cmp(expectedS) != 0 {
+		t.Errorf("%s: Expected S of %X, got %X", f.name, expectedS, s)
+	}
+}
+
+func dsaLoadInt(s string) *big.Int {
+	b, err := hex.DecodeString(s)
+	if err != nil {
+		panic(err)
+	}
+
+	return new(big.Int).SetBytes(b)
+}
diff --git a/ecdsa.go b/ecdsa.go
new file mode 100644
index 0000000..8380cb2
--- /dev/null
+++ b/ecdsa.go
@@ -0,0 +1,54 @@
+package rfc6979
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"math/big"
+)
+
+func hashToInt(hash []byte, c elliptic.Curve) *big.Int {
+	orderBits := c.Params().N.BitLen()
+	orderBytes := (orderBits + 7) / 8
+	if len(hash) > orderBytes {
+		hash = hash[:orderBytes]
+	}
+
+	ret := new(big.Int).SetBytes(hash)
+	excess := len(hash)*8 - orderBits
+	if excess > 0 {
+		ret.Rsh(ret, uint(excess))
+	}
+	return ret
+}
+
+// Sign signs an arbitrary length hash (which should be the result of hashing a
+// larger message) using the private key, priv. It returns the signature as a
+// pair of integers.
+//
+// Note that FIPS 186-3 section 4.6 specifies that the hash should be truncated
+// to the byte-length of the subgroup. This function does not perform that
+// truncation itself.
+func SignECDSA(priv *ecdsa.PrivateKey, hash []byte, alg HashAlgorithm) (r, s *big.Int, err error) {
+	c := priv.PublicKey.Curve
+	N := c.Params().N
+
+	generateSecret(N, priv.D, alg, hash, func(k *big.Int) bool {
+		kInv := new(big.Int).ModInverse(k, N)
+		r, _ = priv.Curve.ScalarBaseMult(k.Bytes())
+		r.Mod(r, N)
+
+		if r.Sign() == 0 {
+			return false
+		}
+
+		e := hashToInt(hash, c)
+		s = new(big.Int).Mul(priv.D, r)
+		s.Add(s, e)
+		s.Mul(s, kInv)
+		s.Mod(s, N)
+
+		return s.Sign() != 0
+	})
+
+	return
+}
diff --git a/ecdsa_test.go b/ecdsa_test.go
new file mode 100644
index 0000000..30daa5d
--- /dev/null
+++ b/ecdsa_test.go
@@ -0,0 +1,441 @@
+package rfc6979
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"math/big"
+	"testing"
+)
+
+type ecdsaFixture struct {
+	name    string
+	key     *ecdsaKey
+	alg     HashAlgorithm
+	message string
+	r, s    string
+}
+
+type ecdsaKey struct {
+	key      *ecdsa.PrivateKey
+	subgroup int
+}
+
+var p224 = &ecdsaKey{
+	key: &ecdsa.PrivateKey{
+		PublicKey: ecdsa.PublicKey{
+			Curve: elliptic.P224(),
+			X:     ecdsaLoadInt("00CF08DA5AD719E42707FA431292DEA11244D64FC51610D94B130D6C"),
+			Y:     ecdsaLoadInt("EEAB6F3DEBE455E3DBF85416F7030CBD94F34F2D6F232C69F3C1385A"),
+		},
+		D: ecdsaLoadInt("F220266E1105BFE3083E03EC7A3A654651F45E37167E88600BF257C1"),
+	},
+	subgroup: 224,
+}
+
+var p256 = &ecdsaKey{
+	key: &ecdsa.PrivateKey{
+		PublicKey: ecdsa.PublicKey{
+			Curve: elliptic.P256(),
+			X:     ecdsaLoadInt("60FED4BA255A9D31C961EB74C6356D68C049B8923B61FA6CE669622E60F29FB6"),
+			Y:     ecdsaLoadInt("7903FE1008B8BC99A41AE9E95628BC64F2F1B20C2D7E9F5177A3C294D4462299"),
+		},
+		D: ecdsaLoadInt("C9AFA9D845BA75166B5C215767B1D6934E50C3DB36E89B127B8A622B120F6721"),
+	},
+	subgroup: 256,
+}
+
+var p384 = &ecdsaKey{
+	key: &ecdsa.PrivateKey{
+		PublicKey: ecdsa.PublicKey{
+			Curve: elliptic.P384(),
+			X:     ecdsaLoadInt("EC3A4E415B4E19A4568618029F427FA5DA9A8BC4AE92E02E06AAE5286B300C64DEF8F0EA9055866064A254515480BC13"),
+			Y:     ecdsaLoadInt("8015D9B72D7D57244EA8EF9AC0C621896708A59367F9DFB9F54CA84B3F1C9DB1288B231C3AE0D4FE7344FD2533264720"),
+		},
+		D: ecdsaLoadInt("6B9D3DAD2E1B8C1C05B19875B6659F4DE23C3B667BF297BA9AA47740787137D896D5724E4C70A825F872C9EA60D2EDF5"),
+	},
+	subgroup: 384,
+}
+
+var p521 = &ecdsaKey{
+	key: &ecdsa.PrivateKey{
+		PublicKey: ecdsa.PublicKey{
+			Curve: elliptic.P521(),
+			X:     ecdsaLoadInt("1894550D0785932E00EAA23B694F213F8C3121F86DC97A04E5A7167DB4E5BCD371123D46E45DB6B5D5370A7F20FB633155D38FFA16D2BD761DCAC474B9A2F5023A4"),
+			Y:     ecdsaLoadInt("0493101C962CD4D2FDDF782285E64584139C2F91B47F87FF82354D6630F746A28A0DB25741B5B34A828008B22ACC23F924FAAFBD4D33F81EA66956DFEAA2BFDFCF5"),
+		},
+		D: ecdsaLoadInt("0FAD06DAA62BA3B25D2FB40133DA757205DE67F5BB0018FEE8C86E1B68C7E75CAA896EB32F1F47C70855836A6D16FCC1466F6D8FBEC67DB89EC0C08B0E996B83538"),
+	},
+	subgroup: 521,
+}
+
+var fixtures = []ecdsaFixture{
+	// ECDSA, 224 Bits (Prime Field)
+	// https://tools.ietf.org/html/rfc6979#appendix-A.2.4
+	ecdsaFixture{
+		name:    "P224/SHA-1 #1",
+		key:     p224,
+		alg:     sha1.New,
+		message: "sample",
+		r:       "22226F9D40A96E19C4A301CE5B74B115303C0F3A4FD30FC257FB57AC",
+		s:       "66D1CDD83E3AF75605DD6E2FEFF196D30AA7ED7A2EDF7AF475403D69",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-224 #1",
+		key:     p224,
+		alg:     sha256.New224,
+		message: "sample",
+		r:       "1CDFE6662DDE1E4A1EC4CDEDF6A1F5A2FB7FBD9145C12113E6ABFD3E",
+		s:       "A6694FD7718A21053F225D3F46197CA699D45006C06F871808F43EBC",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-256 #1",
+		key:     p224,
+		alg:     sha256.New,
+		message: "sample",
+		r:       "61AA3DA010E8E8406C656BC477A7A7189895E7E840CDFE8FF42307BA",
+		s:       "BC814050DAB5D23770879494F9E0A680DC1AF7161991BDE692B10101",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-384 #1",
+		key:     p224,
+		alg:     sha512.New384,
+		message: "sample",
+		r:       "0B115E5E36F0F9EC81F1325A5952878D745E19D7BB3EABFABA77E953",
+		s:       "830F34CCDFE826CCFDC81EB4129772E20E122348A2BBD889A1B1AF1D",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-512 #1",
+		key:     p224,
+		alg:     sha512.New,
+		message: "sample",
+		r:       "074BD1D979D5F32BF958DDC61E4FB4872ADCAFEB2256497CDAC30397",
+		s:       "A4CECA196C3D5A1FF31027B33185DC8EE43F288B21AB342E5D8EB084",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-1 #2",
+		key:     p224,
+		alg:     sha1.New,
+		message: "test",
+		r:       "DEAA646EC2AF2EA8AD53ED66B2E2DDAA49A12EFD8356561451F3E21C",
+		s:       "95987796F6CF2062AB8135271DE56AE55366C045F6D9593F53787BD2",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-224 #2",
+		key:     p224,
+		alg:     sha256.New224,
+		message: "test",
+		r:       "C441CE8E261DED634E4CF84910E4C5D1D22C5CF3B732BB204DBEF019",
+		s:       "902F42847A63BDC5F6046ADA114953120F99442D76510150F372A3F4",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-256 #2",
+		key:     p224,
+		alg:     sha256.New,
+		message: "test",
+		r:       "AD04DDE87B84747A243A631EA47A1BA6D1FAA059149AD2440DE6FBA6",
+		s:       "178D49B1AE90E3D8B629BE3DB5683915F4E8C99FDF6E666CF37ADCFD",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-384 #2",
+		key:     p224,
+		alg:     sha512.New384,
+		message: "test",
+		r:       "389B92682E399B26518A95506B52C03BC9379A9DADF3391A21FB0EA4",
+		s:       "414A718ED3249FF6DBC5B50C27F71F01F070944DA22AB1F78F559AAB",
+	},
+	ecdsaFixture{
+		name:    "P224/SHA-512 #2",
+		key:     p224,
+		alg:     sha512.New,
+		message: "test",
+		r:       "049F050477C5ADD858CAC56208394B5A55BAEBBE887FDF765047C17C",
+		s:       "077EB13E7005929CEFA3CD0403C7CDCC077ADF4E44F3C41B2F60ECFF",
+	},
+	// ECDSA, 256 Bits (Prime Field)
+	// https://tools.ietf.org/html/rfc6979#appendix-A.2.5
+	ecdsaFixture{
+		name:    "P256/SHA-1 #1",
+		key:     p256,
+		alg:     sha1.New,
+		message: "sample",
+		r:       "61340C88C3AAEBEB4F6D667F672CA9759A6CCAA9FA8811313039EE4A35471D32",
+		s:       "6D7F147DAC089441BB2E2FE8F7A3FA264B9C475098FDCF6E00D7C996E1B8B7EB",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-224 #1",
+		key:     p256,
+		alg:     sha256.New224,
+		message: "sample",
+		r:       "53B2FFF5D1752B2C689DF257C04C40A587FABABB3F6FC2702F1343AF7CA9AA3F",
+		s:       "B9AFB64FDC03DC1A131C7D2386D11E349F070AA432A4ACC918BEA988BF75C74C",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-256 #1",
+		key:     p256,
+		alg:     sha256.New,
+		message: "sample",
+		r:       "EFD48B2AACB6A8FD1140DD9CD45E81D69D2C877B56AAF991C34D0EA84EAF3716",
+		s:       "F7CB1C942D657C41D436C7A1B6E29F65F3E900DBB9AFF4064DC4AB2F843ACDA8",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-384 #1",
+		key:     p256,
+		alg:     sha512.New384,
+		message: "sample",
+		r:       "0EAFEA039B20E9B42309FB1D89E213057CBF973DC0CFC8F129EDDDC800EF7719",
+		s:       "4861F0491E6998B9455193E34E7B0D284DDD7149A74B95B9261F13ABDE940954",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-512 #1",
+		key:     p256,
+		alg:     sha512.New,
+		message: "sample",
+		r:       "8496A60B5E9B47C825488827E0495B0E3FA109EC4568FD3F8D1097678EB97F00",
+		s:       "2362AB1ADBE2B8ADF9CB9EDAB740EA6049C028114F2460F96554F61FAE3302FE",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-1 #2",
+		key:     p256,
+		alg:     sha1.New,
+		message: "test",
+		r:       "0CBCC86FD6ABD1D99E703E1EC50069EE5C0B4BA4B9AC60E409E8EC5910D81A89",
+		s:       "01B9D7B73DFAA60D5651EC4591A0136F87653E0FD780C3B1BC872FFDEAE479B1",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-224 #2",
+		key:     p256,
+		alg:     sha256.New224,
+		message: "test",
+		r:       "C37EDB6F0AE79D47C3C27E962FA269BB4F441770357E114EE511F662EC34A692",
+		s:       "C820053A05791E521FCAAD6042D40AEA1D6B1A540138558F47D0719800E18F2D",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-256 #2",
+		key:     p256,
+		alg:     sha256.New,
+		message: "test",
+		r:       "F1ABB023518351CD71D881567B1EA663ED3EFCF6C5132B354F28D3B0B7D38367",
+		s:       "019F4113742A2B14BD25926B49C649155F267E60D3814B4C0CC84250E46F0083",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-384 #2",
+		key:     p256,
+		alg:     sha512.New384,
+		message: "test",
+		r:       "83910E8B48BB0C74244EBDF7F07A1C5413D61472BD941EF3920E623FBCCEBEB6",
+		s:       "8DDBEC54CF8CD5874883841D712142A56A8D0F218F5003CB0296B6B509619F2C",
+	},
+	ecdsaFixture{
+		name:    "P256/SHA-512 #2",
+		key:     p256,
+		alg:     sha512.New,
+		message: "test",
+		r:       "461D93F31B6540894788FD206C07CFA0CC35F46FA3C91816FFF1040AD1581A04",
+		s:       "39AF9F15DE0DB8D97E72719C74820D304CE5226E32DEDAE67519E840D1194E55",
+	},
+	// ECDSA, 384 Bits (Prime Field)
+	// https://tools.ietf.org/html/rfc6979#appendix-A.2.6
+	ecdsaFixture{
+		name:    "P384/SHA-1 #1",
+		key:     p384,
+		alg:     sha1.New,
+		message: "sample",
+		r:       "EC748D839243D6FBEF4FC5C4859A7DFFD7F3ABDDF72014540C16D73309834FA37B9BA002899F6FDA3A4A9386790D4EB2",
+		s:       "A3BCFA947BEEF4732BF247AC17F71676CB31A847B9FF0CBC9C9ED4C1A5B3FACF26F49CA031D4857570CCB5CA4424A443",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-224 #1",
+		key:     p384,
+		alg:     sha256.New224,
+		message: "sample",
+		r:       "42356E76B55A6D9B4631C865445DBE54E056D3B3431766D0509244793C3F9366450F76EE3DE43F5A125333A6BE060122",
+		s:       "9DA0C81787064021E78DF658F2FBB0B042BF304665DB721F077A4298B095E4834C082C03D83028EFBF93A3C23940CA8D",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-256 #1",
+		key:     p384,
+		alg:     sha256.New,
+		message: "sample",
+		r:       "21B13D1E013C7FA1392D03C5F99AF8B30C570C6F98D4EA8E354B63A21D3DAA33BDE1E888E63355D92FA2B3C36D8FB2CD",
+		s:       "F3AA443FB107745BF4BD77CB3891674632068A10CA67E3D45DB2266FA7D1FEEBEFDC63ECCD1AC42EC0CB8668A4FA0AB0",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-384 #1",
+		key:     p384,
+		alg:     sha512.New384,
+		message: "sample",
+		r:       "94EDBB92A5ECB8AAD4736E56C691916B3F88140666CE9FA73D64C4EA95AD133C81A648152E44ACF96E36DD1E80FABE46",
+		s:       "99EF4AEB15F178CEA1FE40DB2603138F130E740A19624526203B6351D0A3A94FA329C145786E679E7B82C71A38628AC8",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-512 #1",
+		key:     p384,
+		alg:     sha512.New,
+		message: "sample",
+		r:       "ED0959D5880AB2D869AE7F6C2915C6D60F96507F9CB3E047C0046861DA4A799CFE30F35CC900056D7C99CD7882433709",
+		s:       "512C8CCEEE3890A84058CE1E22DBC2198F42323CE8ACA9135329F03C068E5112DC7CC3EF3446DEFCEB01A45C2667FDD5",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-1 #2",
+		key:     p384,
+		alg:     sha1.New,
+		message: "test",
+		r:       "4BC35D3A50EF4E30576F58CD96CE6BF638025EE624004A1F7789A8B8E43D0678ACD9D29876DAF46638645F7F404B11C7",
+		s:       "D5A6326C494ED3FF614703878961C0FDE7B2C278F9A65FD8C4B7186201A2991695BA1C84541327E966FA7B50F7382282",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-224 #2",
+		key:     p384,
+		alg:     sha256.New224,
+		message: "test",
+		r:       "E8C9D0B6EA72A0E7837FEA1D14A1A9557F29FAA45D3E7EE888FC5BF954B5E62464A9A817C47FF78B8C11066B24080E72",
+		s:       "07041D4A7A0379AC7232FF72E6F77B6DDB8F09B16CCE0EC3286B2BD43FA8C6141C53EA5ABEF0D8231077A04540A96B66",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-256 #2",
+		key:     p384,
+		alg:     sha256.New,
+		message: "test",
+		r:       "6D6DEFAC9AB64DABAFE36C6BF510352A4CC27001263638E5B16D9BB51D451559F918EEDAF2293BE5B475CC8F0188636B",
+		s:       "2D46F3BECBCC523D5F1A1256BF0C9B024D879BA9E838144C8BA6BAEB4B53B47D51AB373F9845C0514EEFB14024787265",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-384 #2",
+		key:     p384,
+		alg:     sha512.New384,
+		message: "test",
+		r:       "8203B63D3C853E8D77227FB377BCF7B7B772E97892A80F36AB775D509D7A5FEB0542A7F0812998DA8F1DD3CA3CF023DB",
+		s:       "DDD0760448D42D8A43AF45AF836FCE4DE8BE06B485E9B61B827C2F13173923E06A739F040649A667BF3B828246BAA5A5",
+	},
+	ecdsaFixture{
+		name:    "P384/SHA-512 #2",
+		key:     p384,
+		alg:     sha512.New,
+		message: "test",
+		r:       "A0D5D090C9980FAF3C2CE57B7AE951D31977DD11C775D314AF55F76C676447D06FB6495CD21B4B6E340FC236584FB277",
+		s:       "976984E59B4C77B0E8E4460DCA3D9F20E07B9BB1F63BEEFAF576F6B2E8B224634A2092CD3792E0159AD9CEE37659C736",
+	},
+	// ECDSA, 521 Bits (Prime Field)
+	// https://tools.ietf.org/html/rfc6979#appendix-A.2.7
+	ecdsaFixture{
+		name:    "P521/SHA-1 #1",
+		key:     p521,
+		alg:     sha1.New,
+		message: "sample",
+		r:       "0343B6EC45728975EA5CBA6659BBB6062A5FF89EEA58BE3C80B619F322C87910FE092F7D45BB0F8EEE01ED3F20BABEC079D202AE677B243AB40B5431D497C55D75D",
+		s:       "0E7B0E675A9B24413D448B8CC119D2BF7B2D2DF032741C096634D6D65D0DBE3D5694625FB9E8104D3B842C1B0E2D0B98BEA19341E8676AEF66AE4EBA3D5475D5D16",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-224 #1",
+		key:     p521,
+		alg:     sha256.New224,
+		message: "sample",
+		r:       "1776331CFCDF927D666E032E00CF776187BC9FDD8E69D0DABB4109FFE1B5E2A30715F4CC923A4A5E94D2503E9ACFED92857B7F31D7152E0F8C00C15FF3D87E2ED2E",
+		s:       "050CB5265417FE2320BBB5A122B8E1A32BD699089851128E360E620A30C7E17BA41A666AF126CE100E5799B153B60528D5300D08489CA9178FB610A2006C254B41F",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-256 #1",
+		key:     p521,
+		alg:     sha256.New,
+		message: "sample",
+		r:       "1511BB4D675114FE266FC4372B87682BAECC01D3CC62CF2303C92B3526012659D16876E25C7C1E57648F23B73564D67F61C6F14D527D54972810421E7D87589E1A7",
+		s:       "04A171143A83163D6DF460AAF61522695F207A58B95C0644D87E52AA1A347916E4F7A72930B1BC06DBE22CE3F58264AFD23704CBB63B29B931F7DE6C9D949A7ECFC",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-384 #1",
+		key:     p521,
+		alg:     sha512.New384,
+		message: "sample",
+		r:       "1EA842A0E17D2DE4F92C15315C63DDF72685C18195C2BB95E572B9C5136CA4B4B576AD712A52BE9730627D16054BA40CC0B8D3FF035B12AE75168397F5D50C67451",
+		s:       "1F21A3CEE066E1961025FB048BD5FE2B7924D0CD797BABE0A83B66F1E35EEAF5FDE143FA85DC394A7DEE766523393784484BDF3E00114A1C857CDE1AA203DB65D61",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-512 #1",
+		key:     p521,
+		alg:     sha512.New,
+		message: "sample",
+		r:       "0C328FAFCBD79DD77850370C46325D987CB525569FB63C5D3BC53950E6D4C5F174E25A1EE9017B5D450606ADD152B534931D7D4E8455CC91F9B15BF05EC36E377FA",
+		s:       "0617CCE7CF5064806C467F678D3B4080D6F1CC50AF26CA209417308281B68AF282623EAA63E5B5C0723D8B8C37FF0777B1A20F8CCB1DCCC43997F1EE0E44DA4A67A",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-1 #2",
+		key:     p521,
+		alg:     sha1.New,
+		message: "test",
+		r:       "13BAD9F29ABE20DE37EBEB823C252CA0F63361284015A3BF430A46AAA80B87B0693F0694BD88AFE4E661FC33B094CD3B7963BED5A727ED8BD6A3A202ABE009D0367",
+		s:       "1E9BB81FF7944CA409AD138DBBEE228E1AFCC0C890FC78EC8604639CB0DBDC90F717A99EAD9D272855D00162EE9527567DD6A92CBD629805C0445282BBC916797FF",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-224 #2",
+		key:     p521,
+		alg:     sha256.New224,
+		message: "test",
+		r:       "1C7ED902E123E6815546065A2C4AF977B22AA8EADDB68B2C1110E7EA44D42086BFE4A34B67DDC0E17E96536E358219B23A706C6A6E16BA77B65E1C595D43CAE17FB",
+		s:       "177336676304FCB343CE028B38E7B4FBA76C1C1B277DA18CAD2A8478B2A9A9F5BEC0F3BA04F35DB3E4263569EC6AADE8C92746E4C82F8299AE1B8F1739F8FD519A4",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-256 #2",
+		key:     p521,
+		alg:     sha256.New,
+		message: "test",
+		r:       "00E871C4A14F993C6C7369501900C4BC1E9C7B0B4BA44E04868B30B41D8071042EB28C4C250411D0CE08CD197E4188EA4876F279F90B3D8D74A3C76E6F1E4656AA8",
+		s:       "0CD52DBAA33B063C3A6CD8058A1FB0A46A4754B034FCC644766CA14DA8CA5CA9FDE00E88C1AD60CCBA759025299079D7A427EC3CC5B619BFBC828E7769BCD694E86",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-384 #2",
+		key:     p521,
+		alg:     sha512.New384,
+		message: "test",
+		r:       "14BEE21A18B6D8B3C93FAB08D43E739707953244FDBE924FA926D76669E7AC8C89DF62ED8975C2D8397A65A49DCC09F6B0AC62272741924D479354D74FF6075578C",
+		s:       "133330865C067A0EAF72362A65E2D7BC4E461E8C8995C3B6226A21BD1AA78F0ED94FE536A0DCA35534F0CD1510C41525D163FE9D74D134881E35141ED5E8E95B979",
+	},
+	ecdsaFixture{
+		name:    "P521/SHA-512 #2",
+		key:     p521,
+		alg:     sha512.New,
+		message: "test",
+		r:       "13E99020ABF5CEE7525D16B69B229652AB6BDF2AFFCAEF38773B4B7D08725F10CDB93482FDCC54EDCEE91ECA4166B2A7C6265EF0CE2BD7051B7CEF945BABD47EE6D",
+		s:       "1FBD0013C674AA79CB39849527916CE301C66EA7CE8B80682786AD60F98F7E78A19CA69EFF5C57400E3B3A0AD66CE0978214D13BAF4E9AC60752F7B155E2DE4DCE3",
+	},
+}
+
+func TestECDSA(t *testing.T) {
+	for _, f := range fixtures {
+		testEcsaFixture(&f, t)
+	}
+}
+
+func ecdsaLoadInt(s string) (n *big.Int) {
+	n, _ = new(big.Int).SetString(s, 16)
+	return
+}
+
+func testEcsaFixture(f *ecdsaFixture, t *testing.T) {
+	t.Logf("Testing %s", f.name)
+
+	digest := f.alg.digest([]byte(f.message))
+	g := f.key.subgroup / 8
+	if len(digest) > g {
+		digest = digest[0:g]
+	}
+
+	r, s, err := SignECDSA(f.key.key, digest, f.alg)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	expectedR := ecdsaLoadInt(f.r)
+	expectedS := ecdsaLoadInt(f.s)
+
+	if r.Cmp(expectedR) != 0 {
+		t.Errorf("%s: Expected R of %X, got %X", f.name, expectedR, r)
+	}
+
+	if s.Cmp(expectedS) != 0 {
+		t.Errorf("%s: Expected S of %X, got %X", f.name, expectedS, s)
+	}
+}
diff --git a/rfc6979.go b/rfc6979.go
new file mode 100644
index 0000000..1fca958
--- /dev/null
+++ b/rfc6979.go
@@ -0,0 +1,128 @@
+/*
+Paraphrasing RFC6979:
+
+	This package implements a deterministic digital signature generation
+	procedure.  Such signatures are compatible with standard Digital
+	Signature Algorithm (DSA) and Elliptic Curve Digital Signature
+	Algorithm (ECDSA) digital signatures and can be processed with
+	unmodified verifiers, which need not be aware of the procedure
+	described therein.  Deterministic signatures retain the cryptographic
+	security features associated with digital signatures but can be more
+	easily implemented in various environments, since they do not need
+	access to a source of high-quality randomness.
+
+Provides functions similar to crypto/dsa and crypto/ecdsa.
+*/
+package rfc6979
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"hash"
+	"math/big"
+)
+
+// A function which provides a fresh Hash (e.g., sha256.New).
+type HashAlgorithm func() hash.Hash
+
+func (alg HashAlgorithm) digest(m []byte) []byte {
+	h := alg()
+	h.Write(m)
+	return h.Sum(nil)
+}
+
+func (alg HashAlgorithm) mac(k []byte, m []byte) []byte {
+	h := hmac.New(alg, k)
+	h.Write(m)
+	return h.Sum(nil)
+}
+
+// https://tools.ietf.org/html/rfc6979#section-2.3.2
+func bits2int(in []byte, qlen int) *big.Int {
+	vlen := len(in) * 8
+	v := new(big.Int).SetBytes(in)
+	if vlen > qlen {
+		v = new(big.Int).Rsh(v, uint(vlen-qlen))
+	}
+	return v
+}
+
+// https://tools.ietf.org/html/rfc6979#section-2.3.3
+func int2octets(v *big.Int, rolen int) []byte {
+	out := v.Bytes()
+
+	// pad with zeros if it's too short
+	if len(out) < rolen {
+		out2 := make([]byte, rolen)
+		copy(out2[rolen-len(out):], out)
+		return out2
+	}
+
+	// drop most significant bytes if it's too long
+	if len(out) > rolen {
+		out2 := make([]byte, rolen)
+		copy(out2, out[len(out)-rolen:])
+		return out2
+	}
+
+	return out
+}
+
+// https://tools.ietf.org/html/rfc6979#section-2.3.4
+func bits2octets(in []byte, q *big.Int, qlen, rolen int) []byte {
+	z1 := bits2int(in, qlen)
+	z2 := new(big.Int).Sub(z1, q)
+	if z2.Sign() < 0 {
+		return int2octets(z1, rolen)
+	}
+	return int2octets(z2, rolen)
+}
+
+// https://tools.ietf.org/html/rfc6979#section-3.2
+func generateSecret(q, x *big.Int, alg HashAlgorithm, hash []byte, test func(*big.Int) bool) {
+	// Step A
+	qlen := q.BitLen()
+	holen := alg().Size()
+	rolen := (qlen + 7) >> 3
+
+	// Step B
+	v := bytes.Repeat([]byte{0x01}, holen)
+
+	// Step C
+	k := bytes.Repeat([]byte{0x00}, holen)
+
+	// Step D
+	b := int2octets(x, rolen)
+	bh := bits2octets(hash, q, qlen, rolen)
+	bx := append(b, bh...)
+
+	k = alg.mac(k, append(append(v, 0x00), bx...))
+
+	// Step E
+	v = alg.mac(k, v)
+
+	// Step F
+	k = alg.mac(k, append(append(v, 0x01), bx...))
+
+	// Step G
+	v = alg.mac(k, v)
+
+	for {
+		// Step H1
+		t := make([]byte, 0)
+
+		// Step H2
+		for len(t) < qlen/8 {
+			v = alg.mac(k, v)
+			t = append(t, v...)
+		}
+
+		secret := bits2int(t, qlen)
+		if secret.Cmp(big.NewInt(1)) >= 0 && secret.Cmp(q) < 0 && test(secret) {
+			return
+		}
+		k = alg.mac(k, append(v, 0x00))
+		v = alg.mac(k, v)
+
+	}
+}
diff --git a/rfc6979_test.go b/rfc6979_test.go
new file mode 100644
index 0000000..cc91386
--- /dev/null
+++ b/rfc6979_test.go
@@ -0,0 +1,28 @@
+package rfc6979
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"math/big"
+	"testing"
+)
+
+// https://tools.ietf.org/html/rfc6979#appendix-A.1
+func TestGenerateSecret(t *testing.T) {
+	q, _ := new(big.Int).SetString("4000000000000000000020108A2E0CC0D99F8A5EF", 16)
+
+	x, _ := new(big.Int).SetString("09A4D6792295A7F730FC3F2B49CBC0F62E862272F", 16)
+
+	hash, _ := hex.DecodeString("AF2BDBE1AA9B6EC1E2ADE1D694F41FC71A831D0268E9891562113D8A62ADD1BF")
+
+	expected, _ := new(big.Int).SetString("23AF4074C90A02B3FE61D286D5C87F425E6BDD81B", 16)
+	var actual *big.Int
+	generateSecret(q, x, sha256.New, hash, func(k *big.Int) bool {
+		actual = k
+		return true
+	})
+
+	if actual.Cmp(expected) != 0 {
+		t.Errorf("Expected %x, got %x", expected, actual)
+	}
+}