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-rw-r--r--src/lib/pk_pad/iso9796/iso9796.cpp270
1 files changed, 270 insertions, 0 deletions
diff --git a/src/lib/pk_pad/iso9796/iso9796.cpp b/src/lib/pk_pad/iso9796/iso9796.cpp
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index 000000000..db79661e3
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+++ b/src/lib/pk_pad/iso9796/iso9796.cpp
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+/*
+ * ISO-9796-2 - Digital signature schemes giving message recovery schemes 2 and 3
+ * (C) 2016 Tobias Niemann, Hackmanit GmbH
+ *
+ * Botan is released under the Simplified BSD License (see license.txt)
+ */
+
+#include <botan/iso9796.h>
+#include <botan/mgf1.h>
+#include <botan/internal/bit_ops.h>
+#include <botan/hash_id.h>
+
+namespace Botan {
+
+namespace {
+
+secure_vector<byte> iso9796_encoding(const secure_vector<byte>& msg,
+ size_t output_bits, std::unique_ptr<HashFunction>& hash, size_t SALT_SIZE, bool implicit, RandomNumberGenerator& rng)
+ {
+ const size_t output_length = (output_bits + 7) / 8;
+
+ //set trailer length
+ size_t tLength = 1;
+ if(!implicit)
+ {
+ tLength = 2;
+ }
+ const size_t HASH_SIZE = hash->output_length();
+
+ if(output_length <= HASH_SIZE + SALT_SIZE + tLength)
+ {
+ throw Encoding_Error("ISO9796-2::encoding_of: Output length is too small");
+ }
+
+ //calculate message capacity
+ const size_t capacity = output_length
+ - HASH_SIZE - SALT_SIZE - tLength - 1;
+
+ //msg1 is the recoverable and msg2 the unrecoverable message part.
+ secure_vector<byte> msg1;
+ secure_vector<byte> msg2;
+ if(msg.size() > capacity)
+ {
+ msg1 = secure_vector<byte> (msg.begin(), msg.begin() + capacity);
+ msg2 = secure_vector<byte> (msg.begin() + capacity, msg.end());
+ hash->update(msg2);
+ }
+ else
+ {
+ msg1 = msg;
+ }
+ msg2 = hash->final();
+
+ //compute H(C||msg1 ||H(msg2)||S)
+ uint64_t msgLength = msg1.size();
+ secure_vector<byte> salt = rng.random_vec(SALT_SIZE);
+ hash->update_be(msgLength * 8);
+ hash->update(msg1);
+ hash->update(msg2);
+ hash->update(salt);
+ secure_vector<byte> H = hash->final();
+
+ secure_vector<byte> EM(output_length);
+
+ //compute message offset.
+ size_t offset = output_length - HASH_SIZE - SALT_SIZE - tLength
+ - msgLength - 1;
+
+ //insert message border (0x01), msg1 and salt into the output buffer
+ EM[offset] = 0x01;
+ buffer_insert(EM, offset + 1, msg1);
+ buffer_insert(EM, offset + 1 + msgLength, salt);
+
+ //apply mask
+ mgf1_mask(*hash, H.data(), HASH_SIZE, EM.data(),
+ output_length - HASH_SIZE - tLength);
+ buffer_insert(EM, output_length - HASH_SIZE - tLength, H);
+ //set implicit/ISO trailer
+ if(!implicit)
+ {
+ byte hash_id = ieee1363_hash_id(hash->name());
+ if(!hash_id)
+ {
+ throw Encoding_Error("ISO9796-2::encoding_of: no hash identifier for " + hash->name());
+ }
+ EM[output_length - 1] = 0xCC;
+ EM[output_length - 2] = hash_id;
+
+ }
+ else
+ {
+ EM[output_length - 1] = 0xBC;
+ }
+ //clear the leftmost bit (confer bouncy castle)
+ EM[0] &= 0x7F;
+
+ return EM;
+ }
+
+bool iso9796_verification(const secure_vector<byte>& const_coded,
+ const secure_vector<byte>& raw, size_t key_bits, std::unique_ptr<HashFunction>& hash, size_t SALT_SIZE)
+ {
+ const size_t HASH_SIZE = hash->output_length();
+ const size_t KEY_BYTES = (key_bits + 7) / 8;
+
+ if(const_coded.size() != KEY_BYTES)
+ {
+ return false;
+ }
+ //get trailer length
+ size_t tLength;
+ if(const_coded[const_coded.size() - 1] == 0xBC)
+ {
+ tLength = 1;
+ }
+ else
+ {
+ byte hash_id = ieee1363_hash_id(hash->name());
+ if((!const_coded[const_coded.size() - 2]) || (const_coded[const_coded.size() - 2] != hash_id) ||
+ (const_coded[const_coded.size() - 1] != 0xCC))
+ {
+ return false; //in case of wrong ISO trailer.
+ }
+ tLength = 2;
+ }
+
+ secure_vector<byte> coded = const_coded;
+
+ //remove mask
+ byte* DB = coded.data();
+ const size_t DB_size = coded.size() - HASH_SIZE - tLength;
+
+ const byte* H = &coded[DB_size];
+
+ mgf1_mask(*hash, H, HASH_SIZE, DB, DB_size);
+ //clear the leftmost bit (confer bouncy castle)
+ DB[0] &= 0x7F;
+
+ //recover msg1 and salt
+ size_t msg1_offset = 0;
+ for(size_t j = 0; j != DB_size; ++j)
+ {
+ if(DB[j] == 0x01)
+ {
+ msg1_offset = j + 1;
+ break;
+ }
+ }
+ if(msg1_offset == 0)
+ {
+ return false;
+ }
+ secure_vector<byte> msg1(coded.begin() + msg1_offset,
+ coded.end() - tLength - HASH_SIZE - SALT_SIZE);
+ secure_vector<byte> salt(coded.begin() + msg1_offset + msg1.size(),
+ coded.end() - tLength - HASH_SIZE);
+
+ //compute H2(C||msg1||H(msg2)||S*). * indicates a recovered value
+ const size_t capacity = (key_bits - 2 + 7) / 8 - HASH_SIZE
+ - SALT_SIZE - tLength - 1;
+ secure_vector<byte> msg1raw;
+ secure_vector<byte> msg2;
+ if(raw.size() > capacity)
+ {
+ msg1raw = secure_vector<byte> (raw.begin(), raw.begin() + capacity);
+ msg2 = secure_vector<byte> (raw.begin() + capacity, raw.end());
+ hash->update(msg2);
+ }
+ else
+ {
+ msg1raw = raw;
+ }
+ msg2 = hash->final();
+
+ uint64_t msg1rawLength = msg1raw.size();
+ hash->update_be(msg1rawLength * 8);
+ hash->update(msg1raw);
+ hash->update(msg2);
+ hash->update(salt);
+ secure_vector<byte> H3 = hash->final();
+
+ //compute H3(C*||msg1*||H(msg2)||S*) * indicates a recovered value
+ uint64_t msgLength = msg1.size();
+ hash->update_be(msgLength * 8);
+ hash->update(msg1);
+ hash->update(msg2);
+ hash->update(salt);
+ secure_vector<byte> H2 = hash->final();
+
+ //check if H3 == H2
+ return same_mem(H3.data(), H2.data(), HASH_SIZE);
+ }
+
+}
+/*
+ * ISO-9796-2 signature scheme 2
+ * DS 2 is probabilistic
+ */
+void ISO_9796_DS2::update(const byte input[], size_t length)
+ {
+ //need to buffer message completely, before digest
+ m_msg_buffer.insert(m_msg_buffer.end(), input, input+length);
+ }
+
+/*
+ * Return the raw (unencoded) data
+ */
+secure_vector<byte> ISO_9796_DS2::raw_data()
+ {
+ secure_vector<byte> retbuffer = m_msg_buffer;
+ m_msg_buffer.clear();
+ return retbuffer;
+ }
+
+/*
+ * ISO-9796-2 scheme 2 encode operation
+ */
+secure_vector<byte> ISO_9796_DS2::encoding_of(const secure_vector<byte>& msg,
+ size_t output_bits, RandomNumberGenerator& rng)
+ {
+ return iso9796_encoding(msg, output_bits, m_hash, m_SALT_SIZE, m_implicit, rng);
+ }
+
+/*
+ * ISO-9796-2 scheme 2 verify operation
+ */
+bool ISO_9796_DS2::verify(const secure_vector<byte>& const_coded,
+ const secure_vector<byte>& raw, size_t key_bits)
+ {
+ return iso9796_verification(const_coded,raw,key_bits,m_hash,m_SALT_SIZE);
+ }
+
+/*
+ * ISO-9796-2 signature scheme 3
+ * DS 3 is deterministic and equals DS2 without salt
+ */
+void ISO_9796_DS3::update(const byte input[], size_t length)
+ {
+ //need to buffer message completely, before digest
+ m_msg_buffer.insert(m_msg_buffer.end(), input, input+length);
+ }
+
+/*
+ * Return the raw (unencoded) data
+ */
+secure_vector<byte> ISO_9796_DS3::raw_data()
+ {
+ secure_vector<byte> retbuffer = m_msg_buffer;
+ m_msg_buffer.clear();
+ return retbuffer;
+ }
+
+/*
+ * ISO-9796-2 scheme 3 encode operation
+ */
+secure_vector<byte> ISO_9796_DS3::encoding_of(const secure_vector<byte>& msg,
+ size_t output_bits, RandomNumberGenerator& rng)
+ {
+ return iso9796_encoding(msg, output_bits, m_hash, 0, m_implicit, rng);
+ }
+
+/*
+ * ISO-9796-2 scheme 3 verify operation
+ */
+bool ISO_9796_DS3::verify(const secure_vector<byte>& const_coded,
+ const secure_vector<byte>& raw, size_t key_bits)
+ {
+ return iso9796_verification(const_coded, raw, key_bits, m_hash, 0);
+ }
+} \ No newline at end of file
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-30 04:54:56 +0000