-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 E9DXFYs0AoPTKyIx8+CCtMYx9fiLnPTjmy5m1NpTfPjkcsxPNKlFRL0e7Upb9shp
 8FoE0ADDKjF7T6DM5hXj/g==

<SEC-DOCUMENT>0001044321-03-000121.txt : 20030910
<SEC-HEADER>0001044321-03-000121.hdr.sgml : 20030910
<ACCEPTANCE-DATETIME>20030910132837
ACCESSION NUMBER:		0001044321-03-000121
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030908
FILED AS OF DATE:		20030910

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			DATAKEY INC
		CENTRAL INDEX KEY:			0000704914
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS ELECTRICAL MACHINERY, EQUIPMENT & SUPPLIES [3690]
		IRS NUMBER:				411291472
		STATE OF INCORPORATION:			MN
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		407 W TRAVELERS TRAIL
		CITY:			BURNSVILLE
		STATE:			MN
		ZIP:			55337
		BUSINESS PHONE:		6128906850

	MAIL ADDRESS:	
		STREET 1:		407 WEST TRAVELERS TRAIL
		CITY:			BURNSVILLE
		STATE:			MN
		ZIP:			55337

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MARXE AUSTIN W & GREENHOUSE DAVID M
		CENTRAL INDEX KEY:			0001044321

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-11447
		FILM NUMBER:		03889614

	BUSINESS ADDRESS:	
		STREET 1:		153 E 53RD ST
		STREET 2:		55ST FL
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
		BUSINESS PHONE:		2122076500

	MAIL ADDRESS:	
		STREET 1:		153 E 53RD ST
		STREET 2:		55TH FL
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-09-08</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000704914</issuerCik>
        <issuerName>DATAKEY INC</issuerName>
        <issuerTradingSymbol>dkey</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001044321</rptOwnerCik>
            <rptOwnerName>MARXE AUSTIN W &amp; GREENHOUSE DAVID M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>153 E 53RD ST</rptOwnerStreet1>
            <rptOwnerStreet2>55TH FL</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>

        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2003-09-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.6714</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1107141</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Limited Partnerships</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>

        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2003-09-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.6497</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1095141</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Limited Partnerships</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>

    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This is a joint filing by Austin W. Marxe (Marxe) &amp; David M. Greenhouse (Greenhouse). Marxe &amp; Greenhouse share voting and investment control over all securities owned by Special Situations Cayman Fund, L.P. (Cayman), Special Situations Private Equity Fund, L.P. (PE), Special Situations Technology Fund, L.P. (Tech) &amp; Special Situations Technology Fund II, L.P. (Tech2), respectively.  168,166 shares of Common Stock and 166,666 Warrants held by Cayman, 180,500 share of Common Stock and 300,000 Warrants held by PE, 8,675 shares of Common Stock and 35,458 Warrants held by Tech and 54,467 share of Common Stock and 181,209 Warrants held by Tech2. The interest of each of Marxe and Greenhouse in the Common Stock owned by Cayman, PE, Tech and Tech II is limited to the extent of his pecuniary interest, if any, in Cayman, PE, Tech and Tech II, respectively.</footnote>
    </footnotes>


    <ownerSignature>
        <signatureName>Austin W. Marxe</signatureName>
        <signatureDate>2003-09-10</signatureDate>
    </ownerSignature>
    <ownerSignature>
        <signatureName>David M. Greenhouse</signatureName>
        <signatureDate>2003-09-10</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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